DynamicLinqTypeAttribute can now also be defined on an interface (#750)

Author: StefH

src/System.Linq.Dynamic.Core/CustomTypeProviders/DynamicLinqTypeAttribute.cs

@@ -1,10 +1,9 @@
-namespace System.Linq.Dynamic.Core.CustomTypeProviders
+namespace System.Linq.Dynamic.Core.CustomTypeProviders;
+
+/// <summary>
+/// Indicates to Dynamic Linq to consider the Type as a valid dynamic linq type.
+/// </summary>
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Struct | AttributeTargets.Enum, AllowMultiple = false, Inherited = false)]
+public sealed class DynamicLinqTypeAttribute : Attribute
 {
-    /// <summary>
-    /// Indicates to Dynamic Linq to consider the Type as a valid dynamic linq type.
-    /// </summary>
-    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum, AllowMultiple = false, Inherited = false)]
-    public sealed class DynamicLinqTypeAttribute : Attribute
-    {
-    }
-}
+}

test/System.Linq.Dynamic.Core.Tests/DynamicExpressionParserTests.cs

@@ -88,6 +88,17 @@ public class CustomClassWithMethodWithDynamicLinqTypeAttribute
         public int GetAge(int x) => x;
     }
 
+    [DynamicLinqType]
+    public interface ICustomInterfaceWithMethodWithDynamicLinqTypeAttribute
+    {
+        int GetAge(int x);
+    }
+
+    public class CustomClassImplementingInterface : ICustomInterfaceWithMethodWithDynamicLinqTypeAttribute
+    {
+        public int GetAge(int x) => x;
+    }
+
     [DynamicLinqType]
     public class CustomClassWithStaticMethodWithDynamicLinqTypeAttribute
     {
@@ -1057,7 +1068,7 @@ public void DynamicExpressionParser_ParseLambda_CustomStaticMethod_WhenClassHasD
         // Act
         var lambdaExpression = DynamicExpressionParser.ParseLambda(typeof(CustomClassWithStaticMethodWithDynamicLinqTypeAttribute), null, expression);
         var del = lambdaExpression.Compile();
-        var result = (int)del.DynamicInvoke(context);
+        var result = (int?)del.DynamicInvoke(context);
 
         // Assert
         Check.That(result).IsEqualTo(10);
@@ -1073,12 +1084,28 @@ public void DynamicExpressionParser_ParseLambda_CustomMethod_WhenClassHasDynamic
         // Act
         var lambdaExpression = DynamicExpressionParser.ParseLambda(typeof(CustomClassWithMethodWithDynamicLinqTypeAttribute), null, expression);
         var del = lambdaExpression.Compile();
-        var result = (int)del.DynamicInvoke(context);
+        var result = (int?)del.DynamicInvoke(context);
 
         // Assert
         Check.That(result).IsEqualTo(10);
     }
 
+    [Fact]
+    public void DynamicExpressionParser_ParseLambda_CustomInterface_WhenInterfaceHasDynamicLinqTypeAttribute_ShouldWorkCorrect()
+    {
+        // Arrange
+        var context = new CustomClassImplementingInterface();
+        var expression = $"{nameof(ICustomInterfaceWithMethodWithDynamicLinqTypeAttribute.GetAge)}(10)";
+
+        // Act
+        var lambdaExpression = DynamicExpressionParser.ParseLambda(typeof(ICustomInterfaceWithMethodWithDynamicLinqTypeAttribute), null, expression);
+        var del = lambdaExpression.Compile();
+        var result = (int?)del.DynamicInvoke(context);
+
+        // Assert
+        result.Should().Be(10);
+    }
+
     [Fact]
     public void DynamicExpressionParser_ParseLambda_CustomMethod_WhenClassDoesNotHaveDynamicLinqTypeAttribute_ShouldThrowException()
     {