Fix GridReader wiring: use IParameterCallbacks instead of DynamicParameters in QueryMultiple (sync + async)

Dapper/SqlMapper.Async.cs

@@ -1042,7 +1042,7 @@ public static async Task<GridReader> QueryMultipleAsync(this IDbConnection cnn,
                 cmd = command.TrySetupAsyncCommand(cnn, info.ParamReader);
                 reader = await ExecuteReaderWithFlagsFallbackAsync(cmd, wasClosed, CommandBehavior.SequentialAccess, command.CancellationToken).ConfigureAwait(false);
 
-                var result = new GridReader(cmd, reader, identity, command.Parameters as DynamicParameters, command.AddToCache, command.CancellationToken);
+                var result = new GridReader(cmd, reader, identity, command.Parameters as IParameterCallbacks, command.AddToCache, command.CancellationToken);
                 wasClosed = false; // *if* the connection was closed and we got this far, then we now have a reader
                 // with the CloseConnection flag, so the reader will deal with the connection; we
                 // still need something in the "finally" to ensure that broken SQL still results

Dapper/SqlMapper.cs

@@ -1151,7 +1151,7 @@ private static GridReader QueryMultipleImpl(this IDbConnection cnn, ref CommandD
                 cmd = command.SetupCommand(cnn, info.ParamReader);
                 reader = ExecuteReaderWithFlagsFallback(cmd, wasClosed, CommandBehavior.SequentialAccess);
 
-                var result = new GridReader(cmd, reader, identity, command.Parameters as DynamicParameters, command.AddToCache);
+                var result = new GridReader(cmd, reader, identity, command.Parameters as IParameterCallbacks, command.AddToCache);
                 cmd = null; // now owned by result
                 wasClosed = false; // *if* the connection was closed and we got this far, then we now have a reader
                 // with the CloseConnection flag, so the reader will deal with the connection; we

tests/Dapper.Tests/IParameterCallbacksTests.cs

@@ -0,0 +1,71 @@
+using System.Data;
+using System.Threading.Tasks;
+using Microsoft.Data.SqlClient;
+using Xunit;
+
+namespace Dapper.Tests
+{
+    public class IParameterCallbacksTests
+    {
+        class TestParams : SqlMapper.IDynamicParameters, SqlMapper.IParameterCallbacks
+        {
+            public bool Completed { get; private set; }
+
+            public void AddParameters(IDbCommand command, SqlMapper.Identity identity)
+            {
+                // no params needed
+            }
+
+            public void OnCompleted() => Completed = true;
+        }
+
+        [Fact]
+        public void QueryMultiple_Calls_OnCompleted()
+        {
+            if (!TryOpenConnection(out var conn)) return;
+            using var connection = conn!;
+            var p = new TestParams();
+
+            using (var grid = connection.QueryMultiple("select 1; select 2;", p))
+            {
+                var _ = grid.Read<int>();
+                var __ = grid.Read<int>();
+            }
+
+            Assert.True(p.Completed);
+        }
+
+        [Fact]
+        public async Task QueryMultipleAsync_Calls_OnCompleted()
+        {
+            if (!TryOpenConnection(out var conn)) return;
+            using var connection = conn!;
+            var p = new TestParams();
+
+            using (var grid = await connection.QueryMultipleAsync("select 1; select 2;", p))
+            {
+                var _ = await grid.ReadAsync<int>();
+                var __ = await grid.ReadAsync<int>();
+            }
+
+            Assert.True(p.Completed);
+        }
+
+        private static bool TryOpenConnection(out IDbConnection? connection)
+        {
+            connection = null;
+            try
+            {
+                var cs = "Server=localhost,1433;User Id=sa;Password=Str0ngPassw0rd!;TrustServerCertificate=true;";
+                var c = new SqlConnection(cs);
+                c.Open();
+                connection = c;
+                return true;
+            }
+            catch
+            {
+                return false;
+            }
+        }
+    }
+}