C#•2y ago

Incorrect dynamic lambda generation

I have setup a method to dynamically create a lambda to select a parameter and create a new object based on certain fields the code looks like when generated

Param_0 => new MyType() {Amount = Param_0.Amount, Category = Param_0.Category, PaymentMode = Param_0.PaymentMode}

Param_0 => new MyType() {Amount = Param_0.Amount, Category = Param_0.Category, PaymentMode = Param_0.PaymentMode}

but shows an error when using the compiled lambda expression.... here is the code

 public Expression<Func<TSource, object>> DynamicLambda<TSource>
       (ParameterExpression parameterExpression = null, params string[] properties)
        {
            var entityType = typeof(TSource);
            var props = properties.Select(x => entityType.GetProperty(x)).ToList();
            var source = parameterExpression ==null? Expression.Parameter(entityType, "x"): parameterExpression;

            // create x=> new myType{ prop1 = x.prop1,...}
            var newType = CreateNewType(props);
            var binding = props.Select(p => Expression.Bind(newType.GetField(p.Name),
                          Expression.Property(source, p.Name))).ToList();
            var body = Expression.MemberInit(Expression.New(newType), binding);
            var selector = Expression.Lambda<Func<TSource, object>>(body, source);
            return selector;
        }
  public static Type CreateNewType(List<PropertyInfo> props)
        {
            AssemblyName asmName = new AssemblyName("MyAsm");
            AssemblyBuilder dynamicAssembly = AssemblyBuilder
                .DefineDynamicAssembly(asmName, AssemblyBuilderAccess.Run);
            ModuleBuilder dynamicModule = dynamicAssembly.DefineDynamicModule("MyAsm");
            TypeBuilder dynamicAnonymousType = dynamicModule
                .DefineType("MyType", TypeAttributes.Public);

            foreach (var p in props)
            {
                dynamicAnonymousType.DefineField(p.Name, p.PropertyType, FieldAttributes.Public);
            }
            return dynamicAnonymousType.CreateType();
        }

 public Expression<Func<TSource, object>> DynamicLambda<TSource>
       (ParameterExpression parameterExpression = null, params string[] properties)
        {
            var entityType = typeof(TSource);
            var props = properties.Select(x => entityType.GetProperty(x)).ToList();
            var source = parameterExpression ==null? Expression.Parameter(entityType, "x"): parameterExpression;

            // create x=> new myType{ prop1 = x.prop1,...}
            var newType = CreateNewType(props);
            var binding = props.Select(p => Expression.Bind(newType.GetField(p.Name),
                          Expression.Property(source, p.Name))).ToList();
            var body = Expression.MemberInit(Expression.New(newType), binding);
            var selector = Expression.Lambda<Func<TSource, object>>(body, source);
            return selector;
        }
  public static Type CreateNewType(List<PropertyInfo> props)
        {
            AssemblyName asmName = new AssemblyName("MyAsm");
            AssemblyBuilder dynamicAssembly = AssemblyBuilder
                .DefineDynamicAssembly(asmName, AssemblyBuilderAccess.Run);
            ModuleBuilder dynamicModule = dynamicAssembly.DefineDynamicModule("MyAsm");
            TypeBuilder dynamicAnonymousType = dynamicModule
                .DefineType("MyType", TypeAttributes.Public);

            foreach (var p in props)
            {
                dynamicAnonymousType.DefineField(p.Name, p.PropertyType, FieldAttributes.Public);
            }
            return dynamicAnonymousType.CreateType();
        }

1 Reply

PontiacGTX•2y ago

how i call it

_Type.SetQuery(condition.DeserializeObject<FunctionRule>());
                    var items = rule.GetProperty(nameof(value)) ;
                    var values  = items.GetEnumeratorList<string>();
                    var fields = rule.GetProperty(nameof(field)).GetString();
                    return DynamicLambda<T>(parm,properties: values/*.Append(field)*/.ToArray())

_Type.SetQuery(condition.DeserializeObject<FunctionRule>());
                    var items = rule.GetProperty(nameof(value)) ;
                    var values  = items.GetEnumeratorList<string>();
                    var fields = rule.GetProperty(nameof(field)).GetString();
                    return DynamicLambda<T>(parm,properties: values/*.Append(field)*/.ToArray())

the json

{
 "functions": [
    {
      "condition": "select",
      "rules": [
        {
          "label": "Category",
          "field": "Category",
          "parent": "Transaction",
          "operator": "groupby",
          "type": "string",
          "value": [ "Amount", "Category", "PaymentMode" ]
        }
      ]
    }
  ]
  
}

{
 "functions": [
    {
      "condition": "select",
      "rules": [
        {
          "label": "Category",
          "field": "Category",
          "parent": "Transaction",
          "operator": "groupby",
          "type": "string",
          "value": [ "Amount", "Category", "PaymentMode" ]
        }
      ]
    }
  ]
  
}

rule base type

 public class Rule
    {
        [JsonProperty("condition")]
        public string Condition { get; set; }
        [JsonProperty("rules")]
        public  RuleType[] Type { get; set; }
    }

 public class Rule
    {
        [JsonProperty("condition")]
        public string Condition { get; set; }
        [JsonProperty("rules")]
        public  RuleType[] Type { get; set; }
    }

public class RuleType
    {
        [JsonProperty("label")]
        public string Label { get; set; }
        [JsonProperty("field")]
        public string Field { get; set; }
        [JsonProperty("operator")]
        public string Operator { get; set; }
        [JsonProperty("type")]
        public string Type { get; set; }
        [JsonProperty("value")]
        public object Value { get; set; }
        [JsonProperty("parent")]
        public string Parent { get; set; }
    }

public class RuleType
    {
        [JsonProperty("label")]
        public string Label { get; set; }
        [JsonProperty("field")]
        public string Field { get; set; }
        [JsonProperty("operator")]
        public string Operator { get; set; }
        [JsonProperty("type")]
        public string Type { get; set; }
        [JsonProperty("value")]
        public object Value { get; set; }
        [JsonProperty("parent")]
        public string Parent { get; set; }
    }

ok i found that i need to use my assembly name for it to work

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Incorrect dynamic lambda generation