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c#linqlinq-expressions
Roman Koliada
Roman Koliada

Reputation: 5122

How to create Expression<Func<object>> from property name

I want to create an expression like this:

public class Entity
{        
    public virtual long Id { get; set; }
}

Entity alias = null;
Expression<Func<object>> target = () => alias.Id;//have to be created from "Id"

My question is how to create Expression<Func<object>> target programaticaly having string with property name("Id" in this example).

Upvotes: 2

Views: 2776

Answers (1)

Maksim Simkin
Maksim Simkin

Reputation: 9679

OK, I hope, i have finally understood, what do you need :)

I suggest to create such extension method:

public static class EntityExtensions
{
    public static Expression<Func<object>> ToExpression(this Entity entity, string property)
    {
        var constant = Expression.Constant(entity);
        var memberExpression = Expression.Property(constant, property);     
        Expression convertExpr = Expression.Convert(memberExpression, typeof(object));
        var expression = Expression.Lambda(convertExpr);

        return (Expression<Func<object>>)expression;
    }
}

and than call it this way:

var entity = new Entity { Id = 4711 };
var expression = entity.ToExpression("Id");
var result = expression.Compile().DynamicInvoke();

You have to give entity as a parameter.

People, who downvote accepted answer, could explain, what the probem it.

Upvotes: 5

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