Better error message in case property or field is not present in new()

src-console/ConsoleAppEF3.1/Program.cs

@@ -2,13 +2,20 @@
 using System.Linq;
 using ConsoleAppEF2.Database;
 using System.Linq.Dynamic.Core;
+using Newtonsoft.Json;
 
 namespace ConsoleAppEF31
 {
     class Program
     {
         static void Main(string[] args)
         {
+            var users = new[] { new User { FirstName = "Doe" } }.AsQueryable();
+            foreach (dynamic x in users.Select("new (int?(Field) as fld, string(null) as StrNull, string(\"a\") as StrA, string(\"\") as StrEmpty1)"))
+            {
+                Console.WriteLine($"x = {JsonConvert.SerializeObject(x)}");
+            }
+
             var context = new TestContext();
 
             //context.Database.EnsureDeleted();
@@ -60,23 +67,33 @@ static void Main(string[] args)
             }
 
             var config = new ParsingConfig { AllowNewToEvaluateAnyType = true, ResolveTypesBySimpleName = false };
-            var select = context.Cars.Select<Car>(config, $"new {typeof(Car).FullName}(it.Key as Key, \"?\" as Brand)");
+            var select = context.Cars.Select<Car>(config, $"new {typeof(Car).FullName}(it.Key as Key, \"?\" as Brand, string(null) as Color, string(\"e\") as Extra)");
             foreach (Car car in select)
             {
                 Console.WriteLine($"{car.Key}");
             }
 
-            // Users
-            var users = new[] { new User { FirstName = "Doe" } }.AsQueryable();
-
             var resultDynamic = users.Any("c => np(c.FirstName, string.Empty).ToUpper() == \"DOE\"");
             Console.WriteLine(resultDynamic);
 
-            // Fails because Field is not a property but a field!
             var users2 = users.Select<User>(config, "new User(it.FirstName as FirstName, 1 as Field)");
             foreach (User u in users2)
             {
-                Console.WriteLine($"u = {u.FirstName} {u.Field}");
+                Console.WriteLine($"u.FirstName = {u.FirstName}, u.Field = {u.Field}");
+            }
+
+            try
+            {
+                users.Select<User>(config, "new User(1 as FieldDoesNotExist)");
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            foreach (dynamic x in users.Select("new (FirstName, string(\"a\") as StrA, string('c') as StrCh, string(\"\") as StrEmpty1, string('\0') as StrEmpty2, string(null) as StrNull)"))
+            {
+                Console.WriteLine($"x.FirstName = '{x.FirstName}' ; x.Str = '{x.Str == null}'");
             }
         }
 

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

@@ -1455,11 +1455,29 @@ private Expression CreateNewExpression(List<DynamicProperty> properties, List<Ex
             MemberBinding[] bindings = new MemberBinding[properties.Count];
             for (int i = 0; i < bindings.Length; i++)
             {
-                PropertyInfo property = type.GetProperty(properties[i].Name);
-                Type propertyType = property.PropertyType;
+                string propertyOrFieldName = properties[i].Name;
+                Type propertyOrFieldType;
+                MemberInfo memberInfo;
+                PropertyInfo propertyInfo = type.GetProperty(propertyOrFieldName);
+                if (propertyInfo != null)
+                {
+                    memberInfo = propertyInfo;
+                    propertyOrFieldType = propertyInfo.PropertyType;
+                }
+                else
+                {
+                    FieldInfo fieldInfo = type.GetField(propertyOrFieldName);
+                    if (fieldInfo == null)
+                    {
+                        throw ParseError(Res.UnknownPropertyOrField, propertyOrFieldName, TypeHelper.GetTypeName(type));
+                    }
+
+                    memberInfo = fieldInfo;
+                    propertyOrFieldType = fieldInfo.FieldType;
+                }
 
                 // Promote from Type to Nullable Type if needed
-                bindings[i] = Expression.Bind(property, _parsingConfig.ExpressionPromoter.Promote(expressions[i], propertyType, true, true));
+                bindings[i] = Expression.Bind(memberInfo, _parsingConfig.ExpressionPromoter.Promote(expressions[i], propertyOrFieldType, true, true));
             }
 
             return Expression.MemberInit(Expression.New(type), bindings);
@@ -1494,12 +1512,18 @@ Expression ParseTypeAccess(Type type)
                 _textParser.NextToken();
             }
 
-            // This is a shorthand for explicitely converting a string to something
+            // This is a shorthand for explicitly converting a string to something
             bool shorthand = _textParser.CurrentToken.Id == TokenId.StringLiteral;
             if (_textParser.CurrentToken.Id == TokenId.OpenParen || shorthand)
             {
                 Expression[] args = shorthand ? new[] { ParseStringLiteral() } : ParseArgumentList();
 
+                // If only 1 argument, and the arg is ConstantExpression, just return the ConstantExpression
+                if (args.Length == 1 && args[0] is ConstantExpression)
+                {
+                    return args[0];
+                }
+
                 // If only 1 argument, and if the type is a ValueType and argType is also a ValueType, just Convert
                 if (args.Length == 1)
                 {
@@ -1511,7 +1535,10 @@ Expression ParseTypeAccess(Type type)
                     }
                 }
 
-                switch (_methodFinder.FindBestMethod(type.GetConstructors(), args, out MethodBase method))
+                var constructorsWithOutPointerArguments = type.GetConstructors()
+                    .Where(c => !c.GetParameters().Any(p => p.ParameterType.GetTypeInfo().IsPointer))
+                    .ToArray();
+                switch (_methodFinder.FindBestMethod(constructorsWithOutPointerArguments, args, out MethodBase method))
                 {
                     case 0:
                         if (args.Length == 1)

src/System.Linq.Dynamic.Core/Parser/SupportedMethods/MethodFinder.cs

@@ -52,10 +52,10 @@ public int FindMethod(Type type, string methodName, bool staticAccess, Expressio
 
         public int FindBestMethod(IEnumerable<MethodBase> methods, Expression[] args, out MethodBase method)
         {
-            MethodData[] applicable = methods.
-                Select(m => new MethodData { MethodBase = m, Parameters = m.GetParameters() }).
-                Where(m => IsApplicable(m, args)).
-                ToArray();
+            MethodData[] applicable = methods
+                .Select(m => new MethodData { MethodBase = m, Parameters = m.GetParameters() })
+                .Where(m => IsApplicable(m, args))
+                .ToArray();
 
             if (applicable.Length > 1)
             {

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

@@ -69,5 +69,39 @@ public void Parse_ParseAndOperator(string expression, string result)
             // Assert
             Check.That(parsedExpression).Equals(result);
         }
+
+        [Theory]
+        [InlineData("string(null)", null)]
+        [InlineData("string(\"\")", "")]
+        [InlineData("string(\"a\")", "a")]
+        public void Parse_CastStringShouldReturnConstantExpression(string expression, object result)
+        {
+            // Arrange
+            ParameterExpression[] parameters = { ParameterExpressionHelper.CreateParameterExpression(typeof(bool), "x") };
+            var sut = new ExpressionParser(parameters, expression, null, null);
+
+            // Act
+            var constantExpression = (ConstantExpression)sut.Parse(null);
+
+            // Assert
+            Check.That(constantExpression.Value).Equals(result);
+        }
+
+        [Theory]
+        [InlineData("int?(null)", null)]
+        [InlineData("int?(5)", 5)]
+        [InlineData("int(42)", 42)]
+        public void Parse_CastIntShouldReturnConstantExpression(string expression, object result)
+        {
+            // Arrange
+            ParameterExpression[] parameters = { ParameterExpressionHelper.CreateParameterExpression(typeof(bool), "x") };
+            var sut = new ExpressionParser(parameters, expression, null, null);
+
+            // Act
+            var constantExpression = (ConstantExpression)sut.Parse(null);
+
+            // Assert
+            Check.That(constantExpression.Value).Equals(result);
+        }
     }
 }

test/System.Linq.Dynamic.Core.Tests/QueryableTests.Select.cs

@@ -18,6 +18,7 @@ public partial class QueryableTests
     {
         public class Example
         {
+            public int Field;
             public DateTime Time { get; set; }
             public DateTime? TimeNull { get; set; }
             public DayOfWeek? DOWNull { get; set; }
@@ -268,15 +269,27 @@ public void Select_Dynamic_IntoTypeWithNullableProperties2()
             Check.That(resultDynamic.Last()).Equals(result.Last());
         }
 
+        [Fact]
+        public void Select_Dynamic_WithField()
+        {
+            // Arrange
+            var config = new ParsingConfig { AllowNewToEvaluateAnyType = true };
+            var queryable = new List<int> { 1, 2 }.AsQueryable();
+
+            // Act
+            var projectedData = queryable.Select<Example>(config, $"new {typeof(Example).FullName}(~ as Field)");
+
+            // Assert
+            Check.That(projectedData.First().Field).Equals(1);
+            Check.That(projectedData.Last().Field).Equals(2);
+        }
+
         [Fact]
         public void Select_Dynamic_IntoKnownNestedType()
         {
+            // Arrange
             var config = new ParsingConfig { AllowNewToEvaluateAnyType = true };
-#if NETCOREAPP
-            // config.CustomTypeProvider = new NetStandardCustomTypeProvider();
-#endif
-            // Assign
-            var queryable = new List<string>() { "name1", "name2" }.AsQueryable();
+            var queryable = new List<string> { "name1", "name2" }.AsQueryable();
 
             // Act
             var projectedData = queryable.Select<Example.NestedDto>(config, $"new {typeof(Example.NestedDto).FullName}(~ as Name)");
@@ -289,13 +302,9 @@ public void Select_Dynamic_IntoKnownNestedType()
         [Fact]
         public void Select_Dynamic_IntoKnownNestedTypeSecondLevel()
         {
+            // Arrange
             var config = new ParsingConfig { AllowNewToEvaluateAnyType = true };
-#if NETCOREAPP
-            // config.CustomTypeProvider = new NetStandardCustomTypeProvider();
-#endif
-
-            // Assign
-            var queryable = new List<string>() { "name1", "name2" }.AsQueryable();
+            var queryable = new List<string> { "name1", "name2" }.AsQueryable();
 
             // Act
             var projectedData = queryable.Select<Example.NestedDto.NestedDto2>(config, $"new {typeof(Example.NestedDto.NestedDto2).FullName}(~ as Name2)");
@@ -365,6 +374,7 @@ public void Select_Dynamic_Exceptions()
             Assert.Throws<ParseException>(() => qry.Select("new Id, UserName"));
             Assert.Throws<ParseException>(() => qry.Select("new (Id, UserName"));
             Assert.Throws<ParseException>(() => qry.Select("new (Id, UserName, Bad)"));
+            Check.ThatCode(() => qry.Select<User>("new User(it.Bad as Bad)")).Throws<ParseException>().WithMessage("No property or field 'Bad' exists in type 'User'");
 
             Assert.Throws<ArgumentNullException>(() => DynamicQueryableExtensions.Select(null, "Id"));
             Assert.Throws<ArgumentNullException>(() => qry.Select(null));