Blog (pg. 9)

There are a few options already for wrapping calls to Elastic Search (such as ElasticSearch.Net and NEST) however, I wanted to create an object oriented strongly type interface for some simple queries - (with a view to also being able to convert to this from a CDSA "where clause"). My particular implementation of Elastic search, Azure Search, can be called using a restful API interface with OData and Lucene syntax. So my idea was then eventually any OO representation of a query can eventually then be boiled down to a URL with a querystring (similar to how CDSA converts OO clauses to SQL). My first step was to create an abstraction around the concept of a "filter" that can be applied to a search:

public abstract class Filter
{
    public abstract string GetQueryString();
}

Since we are most likely going to be dealing with collections of filters, I created an extension to provide easy access to this method:

internal static class FilterExtensions
{
    public static string AsQueryString(this IEnumerable<Filter> filters)
    {
        return string.Join(" and ", filters.Select(f => f.GetQueryString()));
    }
}

The first concrete implementation is always required by Azure Search, it's the API version you intend to work with:

internal sealed class ApiVersionFilter : Filter
{
    public override string GetQueryString()
    {
        return $"api-version=2016-09-01";
    }
}

Most fields you are querying will either be some filterable scalar value like strings and numbers or collection of these values in a collection column. I represented these types of query using two classes:

public class FieldValuesFilter : Filter
{
    private IEnumerable<IFieldValue> selectedValues;
    private string @operator;

    public FieldValuesFilter(string fieldName, IEnumerable<IFieldValue> selectedValues)
        : this(fieldName, "eq", selectedValues)
    {
    }

    public FieldValuesFilter(string fieldName, string @operator, IEnumerable<IFieldValue> selectedValues)
    {
        this.FieldName = fieldName;
        this.selectedValues = selectedValues;
        this.@operator = @operator;
    }

    public string FieldName { get; private set; }

    public override string GetQueryString()
    {
        return "(" + string.Join(" or ", this.selectedValues.Select(v => $"{this.FieldName} {this.@operator} {v.GetFormattedValue()}")) + ")";
    }
}

public class ArrayValueFilter : Filter
{
    private IEnumerable<IFieldValue> selectedValues;
    private string @operator;

    public ArrayValueFilter(string fieldName, IEnumerable<IFieldValue> selectedValues)
        : this(fieldName, "any", selectedValues)
    {
    }

    public ArrayValueFilter(string fieldName, string @operator, IEnumerable<IFieldValue> selectedValues)
    {
        this.FieldName = fieldName;
        this.selectedValues = selectedValues;
        this.@operator = @operator;
    }

    public string FieldName { get; private set; }

    public override string GetQueryString()
    {
        return "(" + string.Join(" or ", this.selectedValues.Select(v => $"{this.FieldName}/{this.@operator}(t: t eq {v.GetFormattedValue()})")) + ")";
    }
}

You will notice that to abstract the field type I use an interface for IFieldValue for passing in the filter values, this is because depending on whether the data type is a string or a number the formatting will change. The interface and the two implementing classes are below:

public interface IFieldValue
{
    object GetValue();
    string GetFormattedValue();
}

public class StringFieldValue : IFieldValue
{
    private string value;

    public StringFieldValue(string value)
    {
        this.value = value;
    }

    public string GetFormattedValue()
    {
        return $"'{this.value}'";
    }

    public object GetValue()
    {
        return this.value;
    }
}

public class IntegerFieldValue : IFieldValue
{
    private int value;

    public IntegerFieldValue(int value)
    {
        this.value = value;
    }

    public string GetFormattedValue()
    {
        return this.value.ToString();
    }

    public object GetValue()
    {
        return this.value;
    }
}

You can create other filters, such as a "well known text" or "proximity" filter to query spatial data:

public class WktFilter : Filter
{
    private string wkt;

    public WktFilter(string wkt)
    {
        this.Wkt = wkt;
    }

    public string Wkt
    {
        get
        {
            return this.wkt;
        }

        set
        {
            this.wkt = value;
        }
    }

    public override string GetQueryString()
    {
        return $"geo.intersects(location, geography'{this.Wkt}')";
    }
}

public class ProximityFilter : Filter
{
    private double latitude;
    private double longitude;
    private double radiusInMeters;

    public ProximityFilter(double latitude, double longitude, double radiusInMeters)
    {
        this.latitude = latitude;
        this.longitude = longitude;
        this.radiusInMeters = radiusInMeters;
    }

    public override string GetQueryString()
    {
        // Azure Search works with KM not M, so div by 1000
        return $"geo.distance(location, geography'POINT({this.longitude} {this.latitude})') le {this.radiusInMeters / 1000d}";
    }
}

Now that we have the ability to create filters using C# classes and for more derivatives to be added if you more more strong typing, then we need a way of converting this to an Azure Search query. For simplicity I again started with a base class representing a given service which encapsulates the ability to convert a set of filters into a query string or post body and holds the config and endpoint for the index:

public abstract class SearchServiceBase
{
    private readonly AzureServiceConfig config;

    public SearchServiceBase(AzureServiceConfig config)
    {
        this.config = config;
    }

    public abstract string Api { get; }

    public AzureServiceConfig Config
    {
        get
        {
            return this.config;
        }
    }

    protected string GetQueryString(string name, IEnumerable<Filter> filters, int? top, int? skip)
    {
        // parse the input parameters
        StringBuilder requestParameters = new StringBuilder();

        // name param
        if (!string.IsNullOrEmpty(name))
        {
            requestParameters.Append($"search={name}&");
        }

        // add API version by default
        requestParameters.Append(new ApiVersionFilter().GetQueryString() + "&");

        if (top.HasValue)
        {
            requestParameters.Append($"$top={top.Value.ToString()}&");
        }

        if (skip.HasValue)
        {
            requestParameters.Append($"$skip={skip.Value.ToString()}&");
        }

        if (skip.HasValue && skip.Value == 0)
        {
            requestParameters.Append($"$count=true&");
        }

        // filters could be none, one or many
        if (filters != null && filters.Any())
        {
            requestParameters.Append($"$filter={filters.AsQueryString()}&");
        }

        // get the resource
        return requestParameters.Length > 0 ? "?" + requestParameters.ToString().TrimEnd('&') : string.Empty;
    }

    protected string GetPostQueryString()
    {
        return "?" + new ApiVersionFilter().GetQueryString();
    }

    protected string GetPostBody(string name, IEnumerable<Filter> filters, int? top, int? skip)
    {
        // parse the input parameters
        StringWriter sw = new StringWriter();
        JsonTextWriter writer = new JsonTextWriter(sw);

        // {
        writer.WriteStartObject();

        if (skip.HasValue && skip.Value == 0)
        {
            writer.WritePropertyName("count");
            writer.WriteValue("true");
        }

        if (!string.IsNullOrEmpty(name))
        {
            writer.WritePropertyName("search");
            writer.WriteValue(name);

            writer.WritePropertyName("searchMode");
            writer.WriteValue("all");
        }

        if (top.HasValue)
        {
            writer.WritePropertyName("top");
            writer.WriteValue(top.Value.ToString());
        }

        if (skip.HasValue)
        {
            writer.WritePropertyName("skip");
            writer.WriteValue(skip.Value.ToString());
        }

        // filters could be none, one or many
        if (filters != null && filters.Any())
        {
            writer.WritePropertyName("filter");
            writer.WriteValue(filters.AsQueryString());     // querystring is same format as POST property value
        }

        // }
        writer.WriteEndObject();

        return sw.ToString();
    }
}

So an example subclass which consumes this functionality:

public class ExampleSearchService : SearchServiceBase
{
    private readonly string indexName;

    public ExampleSearchService(AzureServiceConfig config, string indexName)
        : base(config)
    {
        this.indexName = indexName;
    }

    public override string Api
    {
        get
        {
            return $"indexes/{this.indexName}/docs/search";
        }
    }

    public async Task<IEnumerable<ExampleSearchResult>> GetResultsAsync(string name, IEnumerable<Filter> filters, int maxResultCount, bool usePost = false)
    {
        using (var webApiClient = new AzureElasticSearchClient(this.Config))
        {
            webApiClient.Timeout = new TimeSpan(0, 20, 0);

            var results = new List<ExampleSearchResult>();

            int pageSize = 1000;
            int pagesToRetrieve = 1;
            int pagesRetrieved = 0;

            // at least one page, but may be more..
            while (pagesRetrieved < pagesToRetrieve)
            {
                HttpResponseMessage result = null;
                if (usePost)
                {
                    string requestUrl = $"{this.Api}{this.GetPostQueryString()}";
                    string requestBody = this.GetPostBody(name, filters, pageSize, pagesRetrieved * pageSize);

                    HttpContent content = new StringContent(requestBody, System.Text.Encoding.UTF8, "application/json");

                    // call the API and increment received count
                    result = await webApiClient.PostAsync(requestUrl, content).ConfigureAwait(false);
                }
                else
                {
                    // build the query url from the filters
                    string requestUrl = $"{this.Api}{this.GetQueryString(name, filters, pageSize, pagesRetreived * pageSize)}";

                    result = await webApiClient.GetAsync(requestUrl).ConfigureAwait(false);
                }
                
                pagesRetrieved++;

                // if it was successful, we can process it
                if (result.IsSuccessStatusCode)
                {
                    // parse the JSON response
                    var jResponse = JObject.Parse(await result.Content.ReadAsStringAsync().ConfigureAwait(false));

                    // if this was the first page, we can parse the item count
                    if (pagesRetrieved == 1)
                    {
                        int count = (int)jResponse.GetValue("@odata.count");

                        // check against max result count and throw exception if over that
                        if (maxResultCount > 0)
                        {
                            if (count > maxResultCount)
                            {
                                throw new InvalidOperationException($"Search result count of {count} was greater than the maximum of {maxResultCount}");
                            }
                        }

                        pagesToRetrieve = (int)Math.Ceiling((double)count / (double)pageSize);
                    }

                    // now get the value, which is the array of results
                    JArray jsonResults = (JArray)jResponse.GetValue("value");

                    // loop over the JSON array and deserialise each result obejct
                    foreach (var resultData in jsonResults)
                    {
                        var result = resultData.ToObject<ExampleSearchResult>();

                        results.Add(result);
                    }
                }
            }

            return results;
        }
    }
}

You will notice I created a wrapper for HttpClient, this is simply to encapsulate adding the base address and API key:

internal class AzureElasticSearchClient : HttpClient
    {
        public AzureElasticSearchClient(AzureServiceConfig config)
        {
            this.BaseAddress = new Uri($"https://{config.AzureSearchServiceName}.search.windows.net/");
            this.DefaultRequestHeaders.Add("api-key", config.AzureSearchApiKey);
        }
    }

Here are some examples of how to create and add filters then call the example search service:

[TestFixture]
public class TestExampleSearchService
{
    private ExampleSearchService sut = new ExampleSearchService();

    [Test]
    public async Task TestGetResultsInWktWithAdditionalFilter_Elastic()
    {
        // arrange
        var testPolygonWkt = "POLYGON ((-1.6259765625 53.74404116282134, -1.6005706787109375 53.76089000834015, -1.5696716308593748 53.73876182109416, -1.6036605834960935 53.72799803200196, -1.6259765625 53.74404116282134))";
        var polyFilter = new WktFilter(testPolygonWkt);
        var examplePropertyFilter = new FieldValuesFilter("SomeIntProperty", new IntegerFieldValue[] { new IntegerFieldValue(1) });
        
        // act
        var startTime = DateTime.Now;
        var result = await this.sut.GetResultsAsync(string.Empty, new Filters.Filter[] { polyFilter, examplePropertyFilter });
        Trace.WriteLine($"Time taken: {DateTime.Now.Subtract(startTime).TotalMilliseconds} ms");
        Trace.WriteLine($"# recs {result.Count()}");
        // assert
        Assert.Greater(result.Count(), 0);
    }

    [Test]
    public async Task TestGetResultsInProximityWithName_Elastic()
    {
        // arrange
        var longi = -1.6259765625;
        var lati = 53.74404116282134;
        var dist = 200;
        var proxFilter = new ProximityFilter(lati, longi, dist);

        // act
        var startTime = DateTime.Now;
        var result = await this.sut.GetResultsAsync("example name", new Filters.Filter[] { proxFilter });

        Trace.WriteLine($"# recs {result.Count()}");
        Trace.WriteLine($"Time taken: {DateTime.Now.Subtract(startTime).TotalMilliseconds} ms");

        // assert
        Assert.Greater(result.Count(), 0);
    }

    [Test]
    public async Task TestGetResultsInArrayFilter_Elastic()
    {
        // arrange
        var possibleValues = {"hello", "world"}.Select(s => new StringFieldValue(s));
        var exampleArrayPropertyFilter = new FieldValuesFilter("SomeStringArrayProperty", possibleValues);
        
        // act
        var startTime = DateTime.Now;
        var result = await this.sut.GetResultsAsync(string.Empty, new Filters.Filter[] { exampleArrayPropertyFilter });
        Trace.WriteLine($"Time taken: {DateTime.Now.Subtract(startTime).TotalMilliseconds} ms");
        Trace.WriteLine($"# recs {result.Count()}");
        // assert
        Assert.Greater(result.Count(), 0);
    }
}

With this structure all now in place, I wanted to plug this into an existing CDSA application which was currently using SQL for performing queries. I therefore needed a way to convert from traditional "CDSA WhereClause" objects to my new Azure Search filter structure. I created a basic implementation, which isn't 100% compatible with all clauses yet, but for most use cases it works fine:

internal class WhereClauseParser
{
    Regex isNumeric = new Regex("^\\d+$");

    public IEnumerable<FieldValuesFilter> ParseWhereClause(WhereClause clause)
    {
        if (clause == null || clause.RecursiveClauseList.Count == 0)
        {
            return null;
        }

        return this.ParseWhereClauseWithSubgroups(clause);
    }

    private IEnumerable<FieldValuesFilter> ParseWhereClauseWithSubgroups(WhereClause clause)
    {
        if (clause.ConjunctionOperator == ConjunctionOperator.And)
        {
            var myFilters = new List<FieldValuesFilter>();
            foreach (var whereClauseElement in clause.ClauseList)
            {
                myFilters.Add(this.ParseWhereClauseElement(whereClauseElement));
            }

            if (clause.SubGroups.Count > 0)
            {
                foreach (var subClause in clause.SubGroups)
                {
                    myFilters.AddRange(this.ParseWhereClauseWithSubgroups(subClause));
                }
            }

            return myFilters;
        }
        else
        {
            throw new NotImplementedException("Elastic search clause parser currently only supports the 'AND' conjunction.");
        }
    }

    private FieldValuesFilter ParseWhereClauseElement(WhereClauseElement whereClauseElement)
    {
        // start with the defaults
        var fieldName = whereClauseElement.CompareItem;
        var values = new object[] { whereClauseElement.CompareValue };

        var @operator = string.Empty;

        // don't need qualified paths, remove the dots
        fieldName = fieldName.Replace(".", "");

        switch (whereClauseElement.Operator)
        {
            case Operator.Equals:
            case Operator.Like: // todo: this should be a wildcard search, not an exact equality
                @operator = "eq";
                break;
            case Operator.NotEqual:
                @operator = "ne";
                break;
            case Operator.GreaterThan:
                @operator = "gt";
                break;
            case Operator.LessThan:
                @operator = "lt";
                break;
            case Operator.GreaterThanEqualTo:
                @operator = "ge";
                break;
            case Operator.LessThanEqualTo:
                @operator = "le";
                break;
            case Operator.In:
                @operator = "eq";
                values = values[0].ToString().Split(',');

                // if it was an array of numbers stored as CSV, then unpack the numbers as ints.
                if (values.All(v => this.isNumeric.IsMatch(v.ToString())))
                {
                    values = values.Select(v => (object) int.Parse(v.ToString())).ToArray();
                }

                break;
            default:
                throw new NotImplementedException("Elastic search clause parser currently does not support this operator");
        }

        return new FieldValuesFilter(fieldName, @operator, values.Select(v => this.FieldValueFactory(v)));

    }

    private IFieldValue FieldValueFactory(object v)
    {
        // a dirty type check, lets call it a "factory"
        if (v is int)
        {
            return new IntegerFieldValue((int)v);
        }
        else
        {
            return new StringFieldValue(v.ToString());
        }
    }
}

Having already been caught out by the ASP.NET deadlock issue when using async code synchronously I did a lot of reading on the subject, from various sources and ended up compiling a list of rules/conventions to follow when dealing with async code. This is by no means a gospel list and I don't elaborate on why each guideline exists, but it's just a concise set of reminders of things to consider when writing async code, since the compiler will not pick up warnings for a lot of these things. The list is shared below:

• Don't use .Result or .Wait() - use async/await (unless absolutely necessary - e.g. destructor, domain value factory - see final point)
• Don't used async void - always return a Task
• Always use "ConfigureAwait(false)" inside async library code (unless you need the context) [NB. Not applicable to .NET Core, bear in mind your consumers for .NET Standard]
• Don't throw parameter exceptions in an async method, make the async method private and check the params in a public Task method before calling the private one
• Don't "await Task.FromResult" - remove the async and just return the Task directly (unless async null or type casting).
• When returning Task, don't return "null" - you must return Task.FromResult<T>(null);
• Make sure any function returning Task is suffixed as "Async" to guide the caller
• Don't use parallel for each with async/await, use tasks and Task.WhenAll (unless need custom partitioning)
• Constructors and destructors cannot be marked async, therefore should not call async methods (no compiler warning)
• For ctors - consider making it a factory with CreateInstanceAsync
• For destructors - try to design against it, or fall back to Task.Run().GetAwaiter().GetResult() syntax (see final point)
• When using .Wait() and .Result syntax, ensure it runs on a background thread with no context e.g. ... Task.Run(() => theMainAsync()).GetAwaiter().GetResult();
  [Technically GetAwaiter().GetResult() is not for public consumption and should be replaced with .Result, however I prefer it because it unwraps exceptions and it shows that you have purposefully coded as blocking code]

General approach: In general, start off by making the interface return Task<> .. update the classes to return Task, then look to see if anything inside the function is truly async. If yes - mark the function async and use await (unless you can pass through).. if No, then just return a Task.FromResult to satisfy the interface.. Don't use async/await inside of a parallel loop. You can block here since its already async and on another thread, or change to tasks. If you *need* to convert to synchronous (such as for passing a value factory) then use Task.Run to encapsulate the blocking call, so that its on another thread with a different context and use .GetAwaiter().GetResult() to unwrap exceptions. I have uploaded some examples to GitHub: https://github.com/craigwardman/AsyncExamples

You can use entity framework to make spatial queries against your Microsoft SQL Server database, which is great when the majority of the ORM code is using EF. What isn't great is that for this to work you have to add some native DLLs into your project, namely the "Microsoft.SqlServer.Types.dll" - this comes in 32 bit and 64 bit variants. Seemingly this also needs to appear in any top level application container, which is usually a different project to the one housing your ORM code. In the end these DLLs seem to get everywhere, except the deployed environment and cause a lot of problems at runtime if they're missing. For my purposes though, I didn't need full in-memory spatial support, I simply wanted to add spatial predicates to my where clauses and return normal "non-spatial" objects back from SQL Server. This is really easy to do in isolation, just write the SQL text and execute it directly using EF. However, most of the time you actually want to combine this with another set of undeterminate predicates which have been applied to the IQueryable in other parts of the code. To solve this issue, I wrote a helper which allows me tag on my spatial query as the last execution step of the IQueryable (e.g. replacing the ToList()) as follows:

internal static class EFSpatialHelper
{
        public static Task<List<T>> QueryByProximityAsync<T>(DbContext context, IQueryable<T> query, Proximity proximity)
        {
            string sqlPointGeogPreamble = $@"
Declare @GeogPoint as geography
Declare @GeogShape as geography

SET @GeogPoint = geography::STGeomFromText('POINT (' + Cast(@longitude as varchar) + ' ' + Cast(@latitude as varchar) + ')', 4326)
SET @GeogShape = @GeogPoint.STBuffer(@buffer)

";
            string sqlGeogPredicate = "@GeogShape.STIntersects(Point) = 1";

            List<SqlParameter> sqlParams = new List<SqlParameter>();
            sqlParams.Add(new SqlParameter("@longitude", proximity.Longitude));
            sqlParams.Add(new SqlParameter("@latitude", proximity.Latitude));
            sqlParams.Add(new SqlParameter("@buffer", proximity.RadiusInMeters));

            return InjectAndExecuteSql(context, query, sqlPointGeogPreamble, sqlGeogPredicate, sqlParams.ToArray());
        }

        internal static Task<List<T>> GetByWellKnownTextAsync<T>(DbContext context, IQueryable<T> query, string wellKnownText)
        {
            string sqlWktGeogPreamble = @"
Declare @GeogPolygon as geography
Declare @GeomPolygon as geometry

Set @GeomPolygon = Geometry::STGeomFromText(@WKT, 4326)
Set @GeogPolygon = Geography::STGeomFromWKB(@GeomPolygon.MakeValid().STUnion(@GeomPolygon.STStartPoint()).STAsBinary(), 4326)

";
            string sqlGeogPredicate = "Point.STIntersects(@GeogPolygon)=1";

            return InjectAndExecuteSql(context, query, sqlWktGeogPreamble, sqlGeogPredicate, new SqlParameter("@WKT", wellKnownText));
        }

        private static Task<List<T>> InjectAndExecuteSql<T>(DbContext context, IQueryable<T> query, string spatialPreamble, string spatialPredicate, params SqlParameter[] spatialParams)
        {
            ObjectQuery<T> objectQuery = GetQueryFromQueryable(query);
            string sqlQryText = $"{spatialPreamble}{objectQuery.ToTraceString()}";

            // the query text in here is quite simple, we know it doesnt have an order by or a group by, so just stick predicates on the end.
            if (!sqlQryText.ToUpper().Contains("WHERE"))
            {
                sqlQryText = $"{sqlQryText} WHERE {spatialPredicate}";
            }
            else
            {
                sqlQryText = $"{Regex.Replace(sqlQryText, "WHERE", "WHERE (", RegexOptions.IgnoreCase)}) AND {spatialPredicate}";
            }

            List<SqlParameter> sqlParams = new List<SqlParameter>();
            if (spatialParams != null)
            {
                sqlParams.AddRange(spatialParams);
            }

            foreach (var p in objectQuery.Parameters)
            {
                sqlParams.Add(new SqlParameter(p.Name, p.Value));
            }

            return context.Database.SqlQuery<T>(
                sqlQryText,
                sqlParams.ToArray()).ToListAsync();
        }

        private static ObjectQuery<T> GetQueryFromQueryable<T>(IQueryable<T> query)
        {
            var internalQueryField = query.GetType().GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).Where(f => f.Name.Equals("_internalQuery")).FirstOrDefault();
            var internalQuery = internalQueryField.GetValue(query);
            var objectQueryField = internalQuery.GetType().GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).Where(f => f.Name.Equals("_objectQuery")).FirstOrDefault();
            return objectQueryField.GetValue(internalQuery) as ObjectQuery<T>;
        }
}

Here is an example of the modified logic for executing a query:

if (wellKnownText != string.Empty)
{
    return await this.GetItemsInWellKnownTextAsync(context, fullQuery, wellKnownText).ConfigureAwait(false);
}
else if (proximity != null)
{
    return await this.GetItemsInProximityAsync(context, fullQuery, proximity).ConfigureAwait(false);
}
else
{
    return await fullQuery.ToListAsync().ConfigureAwait(false);
}

It is possible to create interactive graphical maps in many front end frameworks. In the past I have written mapping applications using Virtual Earth (JavaScript), Bing Maps (Silverlight), Bing Maps (JavaScript) and MapBox (JavaScript). The client side implementations vary, but there are common themes especially from a server side point of view. There are a lot of concepts that be represented in re-usable C# code. For this reason, I have created a class library of ".NET Mapping" objects and helpers, which represent the mapping concepts such as geographical points, bounding boxes, proximities, distance calculation and zoom level calculation. You can view or download the library on GitHub.

Sometimes when using Microsoft Azure AAD for authentication the website goes into a redirect permaloop. So far, this has been caused by two different things for me - so I will collate the causes and solutions below:

1. HTTP vs HTTPS - Since the Microsoft login server is running on HTTPS you must also run your website on HTTPS, since the login cookie will be issued using the secure flag, which prevents it from being read using HTTP. There are various ways to force SSL on your website, from global filters to URL re-writing, but in general make sure to setup your site URLs using HTTPS in the Azure portal and to browse to HTTPS.
2. OWIN Middleware Cookie issue - There is a known issue with the OWIN middleware which means that it's cookies are sometimes lost when issued in conjunction with some other cookie, e.g. the session cookie. The easiest solution to this one I have found is to install a NuGet package called "Kentor.OwinCookieSaver" and then add the following line to startup.auth.cs

   
    public void ConfigureAuth(IAppBuilder app)
           {
               app.SetDefaultSignInAsAuthenticationType(CookieAuthenticationDefaults.AuthenticationType);
               app.UseKentorOwinCookieSaver(); // <-- ADD THIS LINE