LINQ methods respect the configured casing

src/System.Linq.Dynamic.Core/Parser/ExpressionParser.cs

@@ -2139,7 +2139,7 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
         // Create a new innerIt based on the elementType.
         var innerIt = ParameterExpressionHelper.CreateParameterExpression(elementType, string.Empty, _parsingConfig.RenameEmptyParameterExpressionNames);
 
-        if (new[] { "Contains", "ContainsKey", "Skip", "Take" }.Contains(methodName))
+        if (Contains(["Contains", "ContainsKey", "Skip", "Take"], methodName))
         {
             // For any method that acts on the parent element type, we need to specify the outerIt as scope.
             _it = outerIt;
@@ -2194,7 +2194,7 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
         }
 
         Type[] typeArgs;
-        if (new[] { "OfType", "Cast" }.Contains(methodName))
+        if (Contains(["OfType", "Cast"], methodName))
         {
             if (args.Length != 1)
             {
@@ -2204,7 +2204,7 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
             typeArgs = [ResolveTypeFromArgumentExpression(methodName, args[0])];
             args = [];
         }
-        else if (new[] { "Max", "Min", "Select", "OrderBy", "OrderByDescending", "ThenBy", "ThenByDescending", "GroupBy" }.Contains(methodName))
+        else if (Contains(["Max", "Min", "Select", "OrderBy", "OrderByDescending", "ThenBy", "ThenByDescending", "GroupBy"], methodName))
         {
             if (args.Length == 2)
             {
@@ -2219,7 +2219,7 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
                 typeArgs = [elementType];
             }
         }
-        else if (methodName == "SelectMany")
+        else if (Contains(["SelectMany"], methodName))
         {
             var bodyType = Expression.Lambda(args[0], innerIt).Body.Type;
             var interfaces = bodyType.GetInterfaces().Union([bodyType]);
@@ -2238,7 +2238,7 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
         }
         else
         {
-            if (new[] { "Concat", "Contains", "ContainsKey", "DefaultIfEmpty", "Except", "Intersect", "Skip", "Take", "Union", "SequenceEqual" }.Contains(methodName))
+            if (Contains(["Concat", "Contains", "ContainsKey", "DefaultIfEmpty", "Except", "Intersect", "Skip", "Take", "Union", "SequenceEqual"], methodName))
             {
                 args = [instance, args[0]];
             }
@@ -2259,6 +2259,13 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
         return true;
     }
 
+    private bool Contains(string[] haystack, string needle)
+    {
+        return _parsingConfig.IsCaseSensitive 
+            ? haystack.Contains(needle) 
+            : haystack.Any(item => item.Equals(needle, StringComparison.OrdinalIgnoreCase));
+    }
+
     private Type ResolveTypeFromArgumentExpression(string functionName, Expression argumentExpression, int? arguments = null)
     {
         var argument = arguments == null ? string.Empty : arguments == 1 ? "first " : "second ";

test/System.Linq.Dynamic.Core.Tests/Parser/ExpressionParserTests.cs

@@ -471,4 +471,83 @@ public void Parse_InvalidExpressionShouldThrowArgumentException()
         // Assert
         act.Should().Throw<ArgumentException>().WithMessage("Method 'Compare' not found on type 'System.String' or 'System.Int32'");
     }
+
+    [Theory]
+    [InlineData("List.MAX(x => x)", false, "List.Max(Param_0 => Param_0)")]
+    [InlineData("List.min(x => x)", false, "List.Min(Param_0 => Param_0)")]
+    [InlineData("List.Min(x => x)", false, "List.Min(Param_0 => Param_0)")]
+    [InlineData("List.Min(x => x)", true, "List.Min(Param_0 => Param_0)")]
+    [InlineData("List.WHERE(x => x.Ticks >= 100000).max()", false, "List.Where(Param_0 => (Param_0.Ticks >= 100000)).Max()")]
+    public void Parse_LinqMethodsRespectCasing(string expression, bool caseSensitive, string result)
+    {
+        // Arrange
+        var parameters = new[] { Expression.Parameter(typeof(DateTime[]), "List") };
+
+        var parser = new ExpressionParser(
+            parameters,
+            expression, 
+            [],
+            new ParsingConfig
+            {
+                IsCaseSensitive = caseSensitive
+            });
+
+        // Act
+        var parsedExpression = parser.Parse(typeof(DateTime)).ToString();
+
+        // Assert
+        parsedExpression.Should().Be(result);
+    }
+
+    [Fact]
+    public void Parse_InvalidCasingShouldThrowInvalidOperationException()
+    {
+        // Arrange & Act
+        var parameters = new[] { Expression.Parameter(typeof(DateTime[]), "List") };
+
+        Action act = () => new ExpressionParser(
+            parameters,
+            "List.MAX(x => x)", 
+            [],
+            new ParsingConfig
+            {
+                IsCaseSensitive = true
+            })
+            .Parse(typeof(DateTime));
+
+        // Assert
+        act.Should().Throw<InvalidOperationException>().WithMessage("No generic method 'MAX' on type 'System.Linq.Enumerable' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic.*");
+    }
+
+    [Theory]
+    [InlineData("List.max(x => x.max)", "List.Max(Param_0 => Param_0.max)")]
+    [InlineData("List.MAX(x => x.max)", "List.Max(Param_0 => Param_0.max)")]
+    [InlineData("List[0].MAX", "List[0].max")]
+    [InlineData("List.select(max => max.MAX).max()", "List.Select(Param_0 => Param_0.max).Max()")]
+    [InlineData("List.max(max)", "List.Max(Param_0 => Param_0.max)")]
+    public void Parse_LinqMethodsRespectCasingFromModel(string expression, string result)
+    {
+        // Arrange
+        var parameters = new[] { Expression.Parameter(typeof(Model[]), "List") };
+
+        var parser = new ExpressionParser(
+            parameters,
+            expression, 
+            [],
+            new ParsingConfig
+            {
+                IsCaseSensitive = false
+            });
+
+        // Act
+        var parsedExpression = parser.Parse(typeof(DateTime)).ToString();
+
+        // Assert
+        parsedExpression.Should().Be(result);
+    }
+
+    private class Model
+    {
+        public DateTime max { get; set; }
+    }
 }