I want create expression with reflection in c#.
I am target script is:
using (var service = new MyProxy<IProductsService>())
{
var response = service.DoAction<Response<List<Product>>>(srv => srv.GetProducts());
}
How to (srv => srv.GetProducts()
script is generate with expression tree?
Edit:
I am sorry for the wrong expression.
wherein IProductsService, Response<List<Product>>
and GetProducts
are actually unknown types. I take generic on runtime.
I wrote the following methods(CreateExpression) to try. But Expression property = Expression.Call(methodReturnType, methodName.Name, new Type[]{ } ,parameter);
line gives the following error:
No method 'GetProducts' exists on type 'ServiceFoundation.Response
1[System.Collections.Generic.List
1[ServiceFoundation.Products.Product]]'.
Next in line for I have not tested it yet.
Method:
private void CreateExpression(Type interfaceType, Type methodReturnType, MethodInfo methodName)
{
ParameterExpression parameter = Expression.Parameter(interfaceType, "srv");
Expression property = Expression.Call(methodReturnType, methodName.Name, new Type[]{ } ,parameter);
Type expressionType = typeof(Expression<>);
Type lambdaType = typeof(LambdaExpression);
Type funcType = typeof(Func<,>);
Type delegateType = funcType.MakeGenericType(interfaceType, methodReturnType);
Type expression = expressionType.MakeGenericType(delegateType);
MethodInfo mI = typeof(Expression).GetMethod("Lambda");
MethodInfo lambda = mI.MakeGenericMethod(delegateType);
var ex = lambda.Invoke(this, new object[] { delegateType, property, parameter });
}
Hopefully I can express.
I succeeded after a long struggle. I examined different questions here. and in the end I solved this way:
private Expression CreateExpression(Type interfaceType, Type methodReturnType, MethodInfo methodName)
{
ParameterExpression parameter = Expression.Parameter(interfaceType, "srv");
Expression callExpression = Expression.Call(parameter, methodName.Name,null, null);
Type expressionType = typeof(Expression<>);
Type lambdaType = typeof(LambdaExpression);
Type funcType = typeof(Func<,>).MakeGenericType(interfaceType, methodReturnType);
Type expressionGenericType = expressionType.MakeGenericType(funcType);
string methodSignature = "System.Linq.Expressions.LambdaExpression Lambda(System.Linq.Expressions.Expression, System.Linq.Expressions.ParameterExpression[])";
var lambdaMethod = typeof(Expression).GetMethods()
.Single(mi => mi.ToString() == methodSignature);
Expression lambdaExpression = (Expression)lambdaMethod.Invoke(this, new object[] { callExpression, new ParameterExpression[] { parameter } });
return lambdaExpression;
}