#1798 - Added Support for loosely coupled custom query parameters.

Dapper/SqlMapper.cs

@@ -2535,6 +2535,16 @@ internal static IList<LiteralToken> GetLiteralTokens(string sql)
                     il.EmitCall(OpCodes.Callvirt, prop.PropertyType.GetMethod(nameof(ICustomQueryParameter.AddParameter)), null); // stack is now [parameters]
                     continue;
                 }
+                var addParameterMethod = prop.PropertyType.GetMethod(nameof(ICustomQueryParameter.AddParameter), BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic, Type.DefaultBinder, new[] { typeof(IDbCommand), typeof(string) }, null);
+                if (addParameterMethod is not null)
+                {
+                    il.Emit(OpCodes.Ldloc, typedParameterLocal); // stack is now [parameters] [typed-param]
+                    il.Emit(callOpCode, prop.GetGetMethod()); // stack is [parameters] [custom]
+                    il.Emit(OpCodes.Ldarg_0); // stack is now [parameters] [custom] [command]
+                    il.Emit(OpCodes.Ldstr, prop.Name); // stack is now [parameters] [custom] [command] [name]
+                    il.EmitCall(OpCodes.Callvirt, addParameterMethod, null); // stack is now [parameters]
+                    continue;
+                }
 #pragma warning disable 618
                 DbType? dbType = LookupDbType(prop.PropertyType, prop.Name, true, out ITypeHandler handler);
 #pragma warning restore 618

docs/index.md

@@ -24,6 +24,8 @@ Note: to get the latest pre-release build, add ` -Pre` to the end of the command
 
 (note: new PRs will not be merged until they add release note wording here)
 
+- Added Support for loosely coupled custom query parameters (#1798 via robert-io)
+
 ### 2.0.123
 
 - Parameters can now be re-used on subsequent commands (#952 via jamescrowley)

tests/Dapper.Tests/ParameterTests.cs

@@ -58,6 +58,21 @@ public void AddParameter(IDbCommand command, string name)
             }
         }
 
+        public class DbLooselyCoupledCustomParam
+        {
+            private readonly IDbDataParameter _sqlParameter;
+
+            public DbLooselyCoupledCustomParam(IDbDataParameter sqlParameter)
+            {
+                _sqlParameter = sqlParameter;
+            }
+
+            private void AddParameter(IDbCommand command, string name)
+            {
+                command.Parameters.Add(_sqlParameter);
+            }
+        }
+
         private static IEnumerable<IDataRecord> CreateSqlDataRecordList(IDbCommand command, IEnumerable<int> numbers)
         {
             if (command is System.Data.SqlClient.SqlCommand) return CreateSqlDataRecordList_SD(numbers);
@@ -871,8 +886,23 @@ public void TestCustomParameterReuse()
             Assert.Equal(123, result2.Foo);
             Assert.Equal("abc", result2.Bar);
         }
-
-
+
+        [Fact]
+        public void TestLooselyCoupledCustomParameter()
+        {
+            var args = new
+            {
+                foo = new DbLooselyCoupledCustomParam(Provider.CreateRawParameter("foo", 123)),
+                bar = "abc"
+            };
+            var result = connection.Query("select Foo=@foo, Bar=@bar", args).Single();
+            int foo = result.Foo;
+            string bar = result.Bar;
+            Assert.Equal(123, foo);
+            Assert.Equal("abc", bar);
+        }
+
+
         [Fact]
         public void TestDynamicParamNullSupport()
         {