CODEWITHSUNDEEP
c#linq-expressions
Marcos Lommez
Marcos Lommez

Reputation: 136

How to store Expression<Func<T, object>> in a class field?

I would like to store an Expression in class field to be used later.

Here is what i'm trying to do:

public class MyClass
{
    private Expression<Func<Type, object>> _expression;

    public void SetExpression<T>(Expression<Func<T, object>> expression)
    {
        _expression = expression;
    }
}

Upvotes: 0

Views: 1118

Answers (3)

Tristan Trainer
Tristan Trainer

Reputation: 3080

As stated in the comment to the original question by @canton7 you are using <T> and Type but they are not the same thing.

A possible solution for this would be this:

public class MyClass<T>
{
    private Expression<Func<T, object>> _expression;

    public void SetExpression<T>(Expression<Func<T, object>> expression)
    {
        _expression = expression;
    }
}

Using this approach you would need to create the classes using the following 

new MyClass<String>();

This would make the _expression be of type Expression<Func<String, object>>.

If you can't set T to a specific type on creation on the object you will need to pass the expression directly into the method you want to use it in, either that or make the type fixed for the stored Expression.

Upvotes: 2

eocron
eocron

Reputation: 7546

Either create generic class:

public class MyClass<T>
{
    private Expression<Func<T, object>> _expression;

    public void SetExpression(Expression<Func<T, object>> expression)
    {
        _expression = expression;
    }
}

Or use more "abstract" expression:

public class MyClass
{
    private Expression<Func<object, object>> _expression;

    public void SetExpression(Expression<Func<object, object>> expression)
    {
        _expression = expression;
    }
}

In both cases if you working with type of input - you can get it by accessing input arguments of expression:

 var inputTypesWhichIWantedToBeGeneric = _expression.Parameters.Select(x=> x.Type);

Upvotes: 0

Platypus
Platypus

Reputation: 371

Hey is that what you want to achieve ?

public class MyClass<T>
    {
        private Expression<Func<T, object>> _expression;

        public void SetExpression(Expression<Func<T, object>> expression)
        {
            _expression = expression;
        }
    }

Upvotes: 0

Related Questions