Add double type mapping

src/Provider35/EntityFramework.SqlServerCompact35.csproj

@@ -318,6 +318,9 @@
     <Compile Include="..\Provider40\Storage\Internal\SqlCeDecimalTypeMapping.cs">
       <Link>Storage\Internal\SqlCeDecimalTypeMapping.cs</Link>
     </Compile>
+    <Compile Include="..\Provider40\Storage\Internal\SqlCeDoubleTypeMapping.cs">
+      <Link>Storage\Internal\SqlCeDoubleTypeMapping.cs</Link>
+    </Compile>
     <Compile Include="..\Provider40\Storage\Internal\SqlCeFloatTypeMapping.cs">
       <Link>Storage\Internal\SqlCeFloatTypeMapping.cs</Link>
     </Compile>

src/Provider40/EntityFramework.SqlServerCompact40.csproj

@@ -186,6 +186,7 @@
     <Compile Include="MetaData\Conventions\Internal\SqlCeConventionSetBuilder.cs" />
     <Compile Include="Storage\Internal\SqlCeDateTimeTypeMapping.cs" />
     <Compile Include="Storage\Internal\SqlCeDecimalTypeMapping.cs" />
+    <Compile Include="Storage\Internal\SqlCeDoubleTypeMapping.cs" />
     <Compile Include="Storage\Internal\SqlCeFloatTypeMapping.cs" />
     <Compile Include="Storage\Internal\SqlCeLongTypeMapping.cs" />
     <Compile Include="Storage\Internal\SqlCeShortTypeMapping.cs" />

src/Provider40/Storage/Internal/SqlCeDoubleTypeMapping.cs

@@ -0,0 +1,51 @@
+using System.Data;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Storage;
+
+namespace EFCore.SqlCe.Storage.Internal
+{
+    /// <summary>
+    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+    ///     directly from your code. This API may change or be removed in future releases.
+    /// </summary>
+    public class SqlCeDoubleTypeMapping : DoubleTypeMapping
+    {
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        public SqlCeDoubleTypeMapping(
+            [NotNull] string storeType,
+            DbType? dbType = null)
+            : base(storeType, dbType)
+        {
+        }
+
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        protected SqlCeDoubleTypeMapping(RelationalTypeMappingParameters parameters)
+            : base(parameters)
+        {
+        }
+
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        protected override RelationalTypeMapping Clone(RelationalTypeMappingParameters parameters)
+            => new SqlCeDoubleTypeMapping(parameters);
+
+        //TODO Investigate
+
+        //Test 'Microsoft.EntityFrameworkCore.Query.SimpleQuerySqlCeTest.Average_over_nested_subquery_is_client_eval
+
+        ///// <summary>
+        /////     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        /////     directly from your code. This API may change or be removed in future releases.
+        ///// </summary>
+        //protected override string GenerateNonNullSqlLiteral(object value)
+        //    => $"CAST({base.GenerateNonNullSqlLiteral(value)} AS {StoreType})";
+    }
+}

src/Provider40/Storage/Internal/SqlCeTypeMapppingSource.cs

@@ -67,7 +67,7 @@ private readonly SqlCeDateTimeTypeMapping _datetime
             = new SqlCeDateTimeTypeMapping("datetime", dbType: DbType.DateTime);
 
         private readonly DoubleTypeMapping _double
-            = new DoubleTypeMapping("float", DbType.Double);
+            = new SqlCeDoubleTypeMapping("float", DbType.Double);
 
         private readonly GuidTypeMapping _uniqueidentifier
             = new GuidTypeMapping("uniqueidentifier", DbType.Guid);

test/EntityFramework.SqlServerCompact.FunctionalTests/Query/SimpleQuerySqlCeTest.cs

@@ -43,13 +43,6 @@ public override Task OrderBy_coalesce_take_distinct(bool isAsync)
             return base.OrderBy_coalesce_take_distinct(isAsync);
         }
 
-        //TODO ErikEJ Investigate - https://github.com/aspnet/EntityFrameworkCore/issues/13786
-        [Theory(Skip = "Investigate")]
-        public override Task Average_over_nested_subquery_is_client_eval(bool isAsync)
-        {
-            return base.Average_over_nested_subquery_is_client_eval(isAsync);
-        }
-
         [Theory(Skip = "SQLCE limitation")]
         public override async Task Select_bool_closure_with_order_by_property_with_cast_to_nullable(bool isAsync)
         {