when inserting, check if type implements IEnumerable<T> to determine if it's a collection (#880)

* when inserting check if type implements IEnumerable<T> to determine if it's a collection
* when inserting, check if type is a collection by comparing its implemented interfaces to unbound generic type IEnumerable<> instead of the name "IEnumerable`1"

Dapper.Contrib/SqlMapperExtensions.Async.cs

@@ -130,7 +130,7 @@ public static partial class SqlMapperExtensions
                 isList = true;
                 type = type.GetElementType();
             }
-            else if (type.IsGenericType())
+            else if (type.IsGenericType() && type.GetTypeInfo().ImplementedInterfaces.Any(ti => ti.IsGenericType() && ti.GetGenericTypeDefinition() == typeof(IEnumerable<>)))
             {
                 isList = true;
                 type = type.GetGenericArguments()[0];

Dapper.Contrib/SqlMapperExtensions.cs

@@ -295,7 +295,7 @@ private static string GetTableName(Type type)
         }
 
         /// <summary>
-        /// Inserts an entity into table "Ts" and returns identity id or number if inserted rows if inserting a list.
+        /// Inserts an entity into table "Ts" and returns identity id or number of inserted rows if inserting a list.
         /// </summary>
         /// <typeparam name="T">The type to insert.</typeparam>
         /// <param name="connection">Open SqlConnection</param>
@@ -314,7 +314,7 @@ private static string GetTableName(Type type)
                 isList = true;
                 type = type.GetElementType();
             }
-            else if (type.IsGenericType())
+            else if (type.IsGenericType() && type.GetTypeInfo().ImplementedInterfaces.Any(ti => ti.IsGenericType() && ti.GetGenericTypeDefinition() == typeof(IEnumerable<>)))
             {
                 isList = true;
                 type = type.GetGenericArguments()[0];

Dapper.Tests.Contrib/TestSuite.Async.cs

@@ -11,6 +11,41 @@ namespace Dapper.Tests.Contrib
 {
     public abstract partial class TestSuite
     {
+        [Fact]
+        public async Task TypeWithGenericParameterCanBeInsertedAsync()
+        {
+            using (var connection = GetOpenConnection())
+            {
+                await connection.DeleteAllAsync<GenericType<string>>();
+                var objectToInsert = new GenericType<string>
+                {
+                    Id = Guid.NewGuid().ToString(),
+                    Name = "something"
+                };
+                await connection.InsertAsync(objectToInsert);
+
+                Assert.Single(connection.GetAll<GenericType<string>>());
+
+                var objectsToInsert = new List<GenericType<string>>
+                {
+                    new GenericType<string>
+                    {
+                        Id = Guid.NewGuid().ToString(),
+                        Name = "1",
+                    },
+                    new GenericType<string>
+                    {
+                        Id = Guid.NewGuid().ToString(),
+                        Name = "2",
+                    }
+                };
+
+                await connection.InsertAsync(objectsToInsert);
+                var list = connection.GetAll<GenericType<string>>();
+                Assert.Equal(3, list.Count());
+            }
+        }
+
         /// <summary>
         /// Tests for issue #351 
         /// </summary>

Dapper.Tests.Contrib/TestSuite.cs

@@ -85,6 +85,14 @@ public class Result
         public int Order { get; set; }
     }
 
+    [Table("GenericType")]
+    public class GenericType<T>
+    {
+        [ExplicitKey]
+        public string Id { get; set; }
+        public string Name { get; set; }
+    }
+
     public abstract partial class TestSuite
     {
         protected static readonly bool IsAppVeyor = Environment.GetEnvironmentVariable("Appveyor")?.ToUpperInvariant() == "TRUE";
@@ -98,6 +106,41 @@ private IDbConnection GetOpenConnection()
             return connection;
         }
 
+        [Fact]
+        public void TypeWithGenericParameterCanBeInserted()
+        {
+            using (var connection = GetOpenConnection())
+            {
+                connection.DeleteAll<GenericType<string>>();
+                var objectToInsert = new GenericType<string>
+                {
+                    Id = Guid.NewGuid().ToString(),
+                    Name = "something"
+                };
+                connection.Insert(objectToInsert);
+
+                Assert.Single(connection.GetAll<GenericType<string>>());
+
+                var objectsToInsert = new List<GenericType<string>>
+                {
+                    new GenericType<string>
+                    {
+                        Id = Guid.NewGuid().ToString(),
+                        Name = "1",
+                    },
+                    new GenericType<string>
+                    {
+                        Id = Guid.NewGuid().ToString(),
+                        Name = "2",
+                    }
+                };
+
+                connection.Insert(objectsToInsert);
+                var list = connection.GetAll<GenericType<string>>();
+                Assert.Equal(3, list.Count());
+            }
+        }
+
         [Fact]
         public void Issue418()
         {

Dapper.Tests.Contrib/TestSuites.cs

@@ -55,6 +55,8 @@ static SqlServerTestSuite()
                 connection.Execute("CREATE TABLE ObjectY (ObjectYId int not null, Name nvarchar(100) not null);");
                 dropTable("ObjectZ");
                 connection.Execute("CREATE TABLE ObjectZ (Id int not null, Name nvarchar(100) not null);");
+                dropTable("GenericType");
+                connection.Execute("CREATE TABLE GenericType (Id nvarchar(100) not null, Name nvarchar(100) not null);");
             }
         }
     }
@@ -102,6 +104,8 @@ static MySqlServerTestSuite()
                     connection.Execute("CREATE TABLE ObjectY (ObjectYId int not null, Name nvarchar(100) not null);");
                     dropTable("ObjectZ");
                     connection.Execute("CREATE TABLE ObjectZ (Id int not null, Name nvarchar(100) not null);");
+                    dropTable("GenericType");
+                    connection.Execute("CREATE TABLE GenericType (Id nvarchar(100) not null, Name nvarchar(100) not null);");
                 }
             }
             catch (MySqlException e)
@@ -137,6 +141,7 @@ static SQLiteTestSuite()
                 connection.Execute("CREATE TABLE ObjectX (ObjectXId nvarchar(100) not null, Name nvarchar(100) not null) ");
                 connection.Execute("CREATE TABLE ObjectY (ObjectYId integer not null, Name nvarchar(100) not null) ");
                 connection.Execute("CREATE TABLE ObjectZ (Id integer not null, Name nvarchar(100) not null) ");
+                connection.Execute("CREATE TABLE GenericType (Id nvarchar(100) not null, Name nvarchar(100) not null) ");
             }
         }
     }
@@ -167,6 +172,7 @@ static SqlCETestSuite()
                 connection.Execute(@"CREATE TABLE ObjectX (ObjectXId nvarchar(100) not null, Name nvarchar(100) not null) ");
                 connection.Execute(@"CREATE TABLE ObjectY (ObjectYId int not null, Name nvarchar(100) not null) ");
                 connection.Execute(@"CREATE TABLE ObjectZ (Id int not null, Name nvarchar(100) not null) ");
+                connection.Execute(@"CREATE TABLE GenericType (Id nvarchar(100) not null, Name nvarchar(100) not null) ");
             }
             Console.WriteLine("Created database");
         }