Fix #2028

Dapper/SqlMapper.Async.cs

@@ -605,8 +605,7 @@ private static async Task<int> ExecuteMultiImplAsync(IDbConnection cnn, CommandD
                         while (pending.Count != 0)
                         {
                             var pair = pending.Dequeue();
-                            using (pair.Command) { /* dispose commands */ }
-                            total += await pair.Task.ConfigureAwait(false);
+                            using (pair.Command) { total += await pair.Task.ConfigureAwait(false); }
                         }
                     }
                     finally

tests/Dapper.Tests/Providers/SQLServerTests.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Data.Common;
+using System.Threading.Tasks;
+
+namespace Dapper.Tests
+{
+    /// <summary>
+    /// If Docker Desktop is installed, run the following command to start a container suitable for the tests.
+    /// <code>
+    /// docker run -d -p 1433:1433 --name Dapper.Tests.SqlServer -e "ACCEPT_EULA=y" -e "MSSQL_SA_PASSWORD=Pass1234" mcr.microsoft.com/mssql/server:2022-latest
+    /// docker exec Dapper.Tests.SqlServer /opt/mssql-tools18/bin/sqlcmd -Q "CREATE DATABASE tests;" -C -U sa -P Pass1234
+    /// docker exec Dapper.Tests.SqlServer /opt/mssql-tools18/bin/sqlcmd -Q "CREATE LOGIN test WITH PASSWORD='Pass1234';" -C -d tests -U sa -P Pass1234
+    /// docker exec Dapper.Tests.SqlServer /opt/mssql-tools18/bin/sqlcmd -Q "CREATE USER test FOR LOGIN test" -C -d tests -U sa -P Pass1234
+    /// docker exec Dapper.Tests.SqlServer /opt/mssql-tools18/bin/sqlcmd -Q "EXEC sp_addrolemember 'db_owner', 'test';" -C -d tests -U sa -P Pass1234
+    /// </code>
+    /// </summary>
+    public sealed class SqlServerProvider : DatabaseProvider
+    {
+        public override DbProviderFactory Factory => Microsoft.Data.SqlClient.SqlClientFactory.Instance;
+
+        public override string GetConnectionString() =>
+            GetConnectionString("SqlServerConnectionString",
+                "Server=localhost;Database=tests;User ID=test;Password=Pass1234;TrustServerCertificate=true;MultipleActiveResultSets=true");
+
+        public DbConnection GetSqlServerConnection(bool open = true)
+        {
+            string cs = GetConnectionString();
+            var csb = Factory.CreateConnectionStringBuilder()!;
+            csb.ConnectionString = cs;
+            var conn = Factory.CreateConnection()!;
+            conn.ConnectionString = csb.ConnectionString;
+            if (open) conn.Open();
+            return conn;
+        }
+    }
+
+    public class SQLServerTests : TestBase<SqlServerProvider>
+    {
+        [FactSqlServer]
+        public async Task Issue2028_MARS_on_MicrosoftDataSqlClient()
+        {
+            using var conn = Provider.GetSqlServerConnection();
+
+
+            try
+            {
+                conn.Execute("drop table Issue2028_Test");
+            }
+            catch
+            {
+                /* don't care */
+            }
+
+            conn.Execute("create table Issue2028_Test (Id int not null);");
+
+            // insert multiple rows does not throw when using Microsoft.Data.SqlClient and having MultipleActiveRecordsets activated
+            var cmd = new CommandDefinition("insert into Issue2028_Test (Id) values (@id)",
+                new[] { new { id = 1 }, new { id = 2 } }, flags: CommandFlags.Pipelined);
+            await conn.ExecuteAsync(cmd);
+        }
+
+        [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
+        public class FactSqlServerAttribute : FactAttribute
+        {
+            public override string? Skip
+            {
+                get { return unavailable ?? base.Skip; }
+                set { base.Skip = value; }
+            }
+
+            private static readonly string? unavailable;
+
+            static FactSqlServerAttribute()
+            {
+                try
+                {
+                    using (DatabaseProvider<SqlServerProvider>.Instance.GetSqlServerConnection(true))
+                    {
+                        /* just trying to see if it works */
+                    }
+                }
+                catch (Exception ex)
+                {
+                    unavailable = $"SqlServer is unavailable: {ex.Message}";
+                }
+            }
+        }
+    }
+}