I am building a rule checking algorithm that using expression tree, for the type generated using reflection.emit namespace. For some reason i am not able to get it working.
Getting the exception "System.ArgumentException: 'Instance property 'Parameter1' is not defined for type 'System.Object''"
I did try creating dynamic type using expandoObject instead of reflection.emit , it did not work
I appreciate it if anybody can help me to solve the problem. Code sample is given.
using System;
using System.Linq;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
namespace RuleEngine
{
public class RuleEngine
{
public static IEnumerable<RuleOutput> RunRule<T>(IEnumerable<RuleCondition> rules, object targetEntity)
{
IEnumerable<RuleOutput> ruleOutput = null;
foreach (var rule in rules)
{
var ruleDetails = rule.RuleConditionDetails;
rule.RuleConditionDetails.ForEach((item) =>
{
item.ConditionOperatorToApply = GetExpressionOperator(item.ConditionOperator);
});
var compiledRules = CompileRule<T>(rule.RuleConditionDetails);
var foundMatchingRule = compiledRules.All(ruleTemp => ruleTemp(targetEntity));
if (foundMatchingRule)
{
ruleOutput = rule.RuleConditionOutput;
break;
}
}
return ruleOutput;
}
private static List<Func<object, bool>> CompileRule<T>(List<RuleConditionDetails> ruleConditionDetailsList)
{
var compiledRules = new List<Func<object, bool>>();
ruleConditionDetailsList.ForEach(ruleConditionDetails =>
{
var parameterExpression = Expression.Parameter(typeof(T));
var binaryExpression = BuildBinaryExpression<T>(ruleConditionDetails, parameterExpression);
compiledRules.Add(Expression.Lambda<Func<object, bool>>(binaryExpression, parameterExpression).Compile());
});
return compiledRules;
}
private static Expression BuildBinaryExpression<T>(RuleConditionDetails ruleConditionDetails, ParameterExpression parameterExpression)
{
Expression expression = null;
var leftOperand = MemberExpression.Property(parameterExpression, ruleConditionDetails.RuleParameter);
ExpressionType expressionType;
Type operandType = null;
MethodInfo methodInfo = null;
if (ExpressionType.TryParse(ruleConditionDetails.ConditionOperatorToApply, out expressionType))
{
operandType = typeof(T).GetProperty(ruleConditionDetails.RuleParameter).PropertyType;
var rightOperand = Expression.Constant(Convert.ChangeType(ruleConditionDetails.ParameterValue, operandType));
expression = Expression.MakeBinary(expressionType, leftOperand, rightOperand);
}
else
{
if (ruleConditionDetails.ConditionOperatorToApply == "Contains")
{
ruleConditionDetails.ParameterValue = ruleConditionDetails.ParameterValue.ToString().Split(',').ToList();
operandType = Type.GetType("System.Collections.Generic.List`1[System.String]");
methodInfo = operandType.GetMethod(ruleConditionDetails.ConditionOperatorToApply);
var rightOperand = Expression.Constant(Convert.ChangeType(ruleConditionDetails.ParameterValue, operandType));
expression = Expression.Call(rightOperand, methodInfo, leftOperand);
}
}
return expression;
}
private static string GetExpressionOperator(string expressionOperator)
{
string tempOperator = null;
switch (expressionOperator)
{
case "==":
tempOperator = "Equal";
break;
case ">":
tempOperator = "GreaterThan";
break;
case ">=":
tempOperator = "GreaterThanOrEqual";
break;
case "<":
tempOperator = "LessThan";
break;
case "<=":
tempOperator = "LessThanOrEqual";
break;
case "!=":
tempOperator = "NotEqual";
break;
case "IN":
tempOperator = "Contains";
break;
default:
tempOperator = expressionOperator;
break;
}
return tempOperator;
}
}
public class RuleCondition
{
public int RuleId { get; set; }
public List<RuleConditionDetails> RuleConditionDetails { get; set; }
public List<RuleOutput> RuleConditionOutput { get; set; }
}
public class RuleConditionDetails
{
public string RuleParameter { get; set; }
public string ConditionOperator { get; set; }
public object ParameterValue { get; set; }
public string ConditionOperatorToApply { get; set; }
}
public class RuleOutput
{
public string RuleParameter { get; set; }
public object ParameterValue { get; set; }
}
class Program
{
static void Main(string[] args)
{
Dictionary<string, object> keyValues = new Dictionary<string, object>();
keyValues.Add("Parameter1", "XYZ");
keyValues.Add("Parameter2", 999);
var rules = GetRuleCondtions();
IList<PropertyDescriptor> propertyDescriptors = new List<PropertyDescriptor>();
foreach (var item in keyValues)
{
var valueType = item.Value == null ? typeof(string) : item.Value.GetType();
var propertyDescriptor = new PropertyDescriptor(item.Key, valueType);
propertyDescriptors.Add(propertyDescriptor);
}
DynamicClassBuilder dynamicClassBuilder = new DynamicClassBuilder("RuleEngineInputData", propertyDescriptors);
var ruleInputDataObject = dynamicClassBuilder.CreateObject();
RuleEngine.RunRule<Object>(rules, ruleInputDataObject);
Console.ReadKey();
}
private static IList<RuleCondition> GetRuleCondtions()
{
IList<RuleCondition> conditons = new List<RuleCondition>();
conditons.Add(new RuleCondition()
{
RuleConditionDetails = new List<RuleConditionDetails>()
{
new RuleConditionDetails()
{
RuleParameter = "Parameter1",
ConditionOperator = "==",
ParameterValue = "XYZ"
},
new RuleConditionDetails()
{
RuleParameter = "Parameter2",
ConditionOperator = "==",
ParameterValue = "999"
},
},
});
return conditons;
}
}
// Code to create type at runtime
public class DynamicClassBuilder
{
AssemblyName asemblyName = null;
IEnumerable<PropertyDescriptor> propertyDescriptors = null;
public DynamicClassBuilder(string ClassName, IEnumerable<PropertyDescriptor> propertyDescriptors)
{
this.asemblyName = new AssemblyName(ClassName);
this.propertyDescriptors = propertyDescriptors;
}
public Type CreateType()
{
// Create the type builder for creating the class
TypeBuilder typeBuilder = this.GetDynamicTypeBuilder();
// Create the constructor inside the class
CreateConstructor(typeBuilder);
// Create the properties inside the class
foreach (var propertyDescriptor in propertyDescriptors)
{
CreateProperty(typeBuilder, propertyDescriptor.PropertyName, propertyDescriptor.PropertyType);
}
// Create class
Type type = typeBuilder.CreateTypeInfo();
return type;
}
public object CreateObject()
{
// Create the type builder for creating the class
TypeBuilder typeBuilder = this.GetDynamicTypeBuilder();
// Create the constructor inside the class
CreateConstructor(typeBuilder);
// Create the properties inside the class
foreach (var propertyDescriptor in propertyDescriptors)
{
CreateProperty(typeBuilder, propertyDescriptor.PropertyName, propertyDescriptor.PropertyType);
}
// Create class
Type type = typeBuilder.CreateTypeInfo();
return Activator.CreateInstance(type);
}
private TypeBuilder GetDynamicTypeBuilder()
{
AssemblyBuilder assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(this.asemblyName, AssemblyBuilderAccess.Run);
ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("MainModule");
TypeBuilder typeBuilder = moduleBuilder.DefineType(this.asemblyName.FullName
, TypeAttributes.Public |
TypeAttributes.Class |
TypeAttributes.AutoClass |
TypeAttributes.AnsiClass |
TypeAttributes.BeforeFieldInit |
TypeAttributes.AutoLayout
, null);
//typeBuilder.SetParent(typeof(RuleEngineInputDataBase));
return typeBuilder;
}
private void CreateConstructor(TypeBuilder typeBuilder)
{
typeBuilder.DefineDefaultConstructor(MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName);
}
private void CreateProperty(TypeBuilder typeBuilder, string propertyName, Type propertyType)
{
FieldBuilder fieldBuilder = typeBuilder.DefineField("_" + propertyName, propertyType, FieldAttributes.Private);
PropertyBuilder propertyBuilder = typeBuilder.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null);
MethodBuilder getPropMthdBldr = typeBuilder.DefineMethod("get_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType, Type.EmptyTypes);
ILGenerator getILGenerator = getPropMthdBldr.GetILGenerator();
getILGenerator.Emit(OpCodes.Ldarg_0);
getILGenerator.Emit(OpCodes.Ldfld, fieldBuilder);
getILGenerator.Emit(OpCodes.Ret);
MethodBuilder setMethodBuilder = typeBuilder.DefineMethod("set_" + propertyName,
MethodAttributes.Public |
MethodAttributes.SpecialName |
MethodAttributes.HideBySig,
null, new[] { propertyType });
ILGenerator setILGenerator = setMethodBuilder.GetILGenerator();
Label modifyProperty = setILGenerator.DefineLabel();
Label exitSet = setILGenerator.DefineLabel();
setILGenerator.MarkLabel(modifyProperty);
setILGenerator.Emit(OpCodes.Ldarg_0);
setILGenerator.Emit(OpCodes.Ldarg_1);
setILGenerator.Emit(OpCodes.Stfld, fieldBuilder);
setILGenerator.Emit(OpCodes.Nop);
setILGenerator.MarkLabel(exitSet);
setILGenerator.Emit(OpCodes.Ret);
propertyBuilder.SetGetMethod(getPropMthdBldr);
propertyBuilder.SetSetMethod(setMethodBuilder);
}
public object SetPropertyValues(object accessor, IDictionary<string, object> ruleInputData)
{
Type accessorType = accessor.GetType();
foreach (PropertyInfo propertyInfo in accessorType.GetProperties())
{
object propertyValue = null;
if (ruleInputData.TryGetValue(propertyInfo.Name, out propertyValue))
{
if (propertyInfo.CanRead)
{
propertyValue = Convert.ChangeType(propertyValue, propertyInfo.PropertyType);
propertyInfo.SetValue(accessor, propertyValue);
}
}
}
return accessor;
}
}
}
I have found few issues. First of all, methods should not be generic. You set T to object anyway. Instead you should get entity type from ruleInputDataObject (ruleInputDataObject.GetType()).
Another problem is the way you're creating lambda in CompileRule method. You pass want to have lambda with Func<object, bool> signature and access properties from generated type. This won't work unless you cast parameterExpression to entity type.
Here is fixed code:
namespace RuleEngine
{
public class PropertyDescriptor
{
public string PropertyName { get; }
public Type PropertyType { get; }
public PropertyDescriptor(string propertyName, Type propertyType)
{
PropertyName = propertyName;
PropertyType = propertyType;
}
}
public class RuleEngine
{
public static IEnumerable<RuleOutput> RunRule(IEnumerable<RuleCondition> rules, object targetEntity)
{
Type entityType = targetEntity.GetType();
IEnumerable<RuleOutput> ruleOutput = null;
foreach (var rule in rules)
{
var ruleDetails = rule.RuleConditionDetails;
rule.RuleConditionDetails.ForEach((item) =>
{
item.ConditionOperatorToApply = GetExpressionOperator(item.ConditionOperator);
});
var compiledRules = CompileRule(rule.RuleConditionDetails, entityType);
var foundMatchingRule = compiledRules.All(ruleTemp => ruleTemp(targetEntity));
if (foundMatchingRule)
{
ruleOutput = rule.RuleConditionOutput;
break;
}
}
return ruleOutput;
}
private static List<Func<object, bool>> CompileRule(List<RuleConditionDetails> ruleConditionDetailsList,
Type entityType)
{
var compiledRules = new List<Func<object, bool>>();
ruleConditionDetailsList.ForEach(ruleConditionDetails =>
{
var parameterExpression = Expression.Parameter(typeof(object));
var entityExpression = Expression.Convert(parameterExpression, entityType);
var binaryExpression = BuildBinaryExpression(ruleConditionDetails, entityExpression, entityType);
compiledRules.Add(
Expression.Lambda<Func<object, bool>>(binaryExpression, parameterExpression).Compile());
});
return compiledRules;
}
private static Expression BuildBinaryExpression(RuleConditionDetails ruleConditionDetails,
Expression parameterExpression, Type entityType)
{
Expression expression = null;
var leftOperand = MemberExpression.Property(parameterExpression, ruleConditionDetails.RuleParameter);
ExpressionType expressionType;
Type operandType = null;
MethodInfo methodInfo = null;
if (ExpressionType.TryParse(ruleConditionDetails.ConditionOperatorToApply, out expressionType))
{
operandType = entityType.GetProperty(ruleConditionDetails.RuleParameter).PropertyType;
var rightOperand =
Expression.Constant(Convert.ChangeType(ruleConditionDetails.ParameterValue, operandType));
expression = Expression.MakeBinary(expressionType, leftOperand, rightOperand);
}
else
{
if (ruleConditionDetails.ConditionOperatorToApply == "Contains")
{
ruleConditionDetails.ParameterValue =
ruleConditionDetails.ParameterValue.ToString().Split(',').ToList();
operandType = Type.GetType("System.Collections.Generic.List`1[System.String]");
methodInfo = operandType.GetMethod(ruleConditionDetails.ConditionOperatorToApply);
var rightOperand =
Expression.Constant(Convert.ChangeType(ruleConditionDetails.ParameterValue, operandType));
expression = Expression.Call(rightOperand, methodInfo, leftOperand);
}
}
return expression;
}
private static string GetExpressionOperator(string expressionOperator)
{
string tempOperator = null;
switch (expressionOperator)
{
case "==":
tempOperator = "Equal";
break;
case ">":
tempOperator = "GreaterThan";
break;
case ">=":
tempOperator = "GreaterThanOrEqual";
break;
case "<":
tempOperator = "LessThan";
break;
case "<=":
tempOperator = "LessThanOrEqual";
break;
case "!=":
tempOperator = "NotEqual";
break;
case "IN":
tempOperator = "Contains";
break;
default:
tempOperator = expressionOperator;
break;
}
return tempOperator;
}
}
public class RuleCondition
{
public int RuleId { get; set; }
public List<RuleConditionDetails> RuleConditionDetails { get; set; }
public List<RuleOutput> RuleConditionOutput { get; set; }
}
public class RuleConditionDetails
{
public string RuleParameter { get; set; }
public string ConditionOperator { get; set; }
public object ParameterValue { get; set; }
public string ConditionOperatorToApply { get; set; }
}
public class RuleOutput
{
public string RuleParameter { get; set; }
public object ParameterValue { get; set; }
}
class Program
{
static void Main(string[] args)
{
Dictionary<string, object> keyValues = new Dictionary<string, object>();
keyValues.Add("Parameter1", "XYZ");
keyValues.Add("Parameter2", 999);
var rules = GetRuleCondtions();
IList<PropertyDescriptor> propertyDescriptors = new List<PropertyDescriptor>();
foreach (var item in keyValues)
{
var valueType = item.Value == null ? typeof(string) : item.Value.GetType();
var propertyDescriptor = new PropertyDescriptor(item.Key, valueType);
propertyDescriptors.Add(propertyDescriptor);
}
DynamicClassBuilder dynamicClassBuilder =
new DynamicClassBuilder("RuleEngineInputData", propertyDescriptors);
var ruleInputDataObject = dynamicClassBuilder.CreateObject();
RuleEngine.RunRule(rules, ruleInputDataObject);
Console.ReadKey();
}
private static IList<RuleCondition> GetRuleCondtions()
{
IList<RuleCondition> conditons = new List<RuleCondition>();
conditons.Add(new RuleCondition()
{
RuleConditionDetails = new List<RuleConditionDetails>()
{
new RuleConditionDetails()
{
RuleParameter = "Parameter1",
ConditionOperator = "==",
ParameterValue = "XYZ"
},
new RuleConditionDetails()
{
RuleParameter = "Parameter2",
ConditionOperator = "==",
ParameterValue = "999"
},
},
});
return conditons;
}
}
// Code to create type at runtime
public class DynamicClassBuilder
{
AssemblyName asemblyName = null;
IEnumerable<PropertyDescriptor> propertyDescriptors = null;
public DynamicClassBuilder(string ClassName, IEnumerable<PropertyDescriptor> propertyDescriptors)
{
this.asemblyName = new AssemblyName(ClassName);
this.propertyDescriptors = propertyDescriptors;
}
public Type CreateType()
{
// Create the type builder for creating the class
TypeBuilder typeBuilder = this.GetDynamicTypeBuilder();
// Create the constructor inside the class
CreateConstructor(typeBuilder);
// Create the properties inside the class
foreach (var propertyDescriptor in propertyDescriptors)
{
CreateProperty(typeBuilder, propertyDescriptor.PropertyName, propertyDescriptor.PropertyType);
}
// Create class
Type type = typeBuilder.CreateTypeInfo();
return type;
}
public object CreateObject()
{
// Create the type builder for creating the class
TypeBuilder typeBuilder = this.GetDynamicTypeBuilder();
// Create the constructor inside the class
CreateConstructor(typeBuilder);
// Create the properties inside the class
foreach (var propertyDescriptor in propertyDescriptors)
{
CreateProperty(typeBuilder, propertyDescriptor.PropertyName, propertyDescriptor.PropertyType);
}
// Create class
Type type = typeBuilder.CreateTypeInfo();
return Activator.CreateInstance(type);
}
private TypeBuilder GetDynamicTypeBuilder()
{
AssemblyBuilder assemblyBuilder =
AssemblyBuilder.DefineDynamicAssembly(this.asemblyName, AssemblyBuilderAccess.Run);
ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("MainModule");
TypeBuilder typeBuilder = moduleBuilder.DefineType(this.asemblyName.FullName
, TypeAttributes.Public |
TypeAttributes.Class |
TypeAttributes.AutoClass |
TypeAttributes.AnsiClass |
TypeAttributes.BeforeFieldInit |
TypeAttributes.AutoLayout
, null);
//typeBuilder.SetParent(typeof(RuleEngineInputDataBase));
return typeBuilder;
}
private void CreateConstructor(TypeBuilder typeBuilder)
{
typeBuilder.DefineDefaultConstructor(MethodAttributes.Public | MethodAttributes.SpecialName |
MethodAttributes.RTSpecialName);
}
private void CreateProperty(TypeBuilder typeBuilder, string propertyName, Type propertyType)
{
FieldBuilder fieldBuilder =
typeBuilder.DefineField("_" + propertyName, propertyType, FieldAttributes.Private);
PropertyBuilder propertyBuilder =
typeBuilder.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, null);
MethodBuilder getPropMthdBldr = typeBuilder.DefineMethod("get_" + propertyName,
MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType,
Type.EmptyTypes);
ILGenerator getILGenerator = getPropMthdBldr.GetILGenerator();
getILGenerator.Emit(OpCodes.Ldarg_0);
getILGenerator.Emit(OpCodes.Ldfld, fieldBuilder);
getILGenerator.Emit(OpCodes.Ret);
MethodBuilder setMethodBuilder = typeBuilder.DefineMethod("set_" + propertyName,
MethodAttributes.Public |
MethodAttributes.SpecialName |
MethodAttributes.HideBySig,
null, new[] {propertyType});
ILGenerator setILGenerator = setMethodBuilder.GetILGenerator();
Label modifyProperty = setILGenerator.DefineLabel();
Label exitSet = setILGenerator.DefineLabel();
setILGenerator.MarkLabel(modifyProperty);
setILGenerator.Emit(OpCodes.Ldarg_0);
setILGenerator.Emit(OpCodes.Ldarg_1);
setILGenerator.Emit(OpCodes.Stfld, fieldBuilder);
setILGenerator.Emit(OpCodes.Nop);
setILGenerator.MarkLabel(exitSet);
setILGenerator.Emit(OpCodes.Ret);
propertyBuilder.SetGetMethod(getPropMthdBldr);
propertyBuilder.SetSetMethod(setMethodBuilder);
}
public object SetPropertyValues(object accessor, IDictionary<string, object> ruleInputData)
{
Type accessorType = accessor.GetType();
foreach (PropertyInfo propertyInfo in accessorType.GetProperties())
{
object propertyValue = null;
if (ruleInputData.TryGetValue(propertyInfo.Name, out propertyValue))
{
if (propertyInfo.CanRead)
{
propertyValue = Convert.ChangeType(propertyValue, propertyInfo.PropertyType);
propertyInfo.SetValue(accessor, propertyValue);
}
}
}
return accessor;
}
}
}