Reflection - get property name [duplicate]

Question

I'd like to pass property names to a function without using of magic strings.

Something like:

Get<ObjectType>(x=>x.Property1);

where Property1 is a property of type ObjectType.

What would the method implementation look like ?

Answer 1

This can be achieved using Expressions:

// requires object instance, but you can skip specifying T static string GetPropertyName<T>(Expression<Func<T>> exp) {     return (((MemberExpression)(exp.Body)).Member).Name; }  // requires explicit specification of both object type and property type static string GetPropertyName<TObject, TResult>(Expression<Func<TObject, TResult>> exp) {     // extract property name     return (((MemberExpression)(exp.Body)).Member).Name; }  // requires explicit specification of object type static string GetPropertyName<TObject>(Expression<Func<TObject, object>> exp) {     var body = exp.Body;     var convertExpression = body as UnaryExpression;     if(convertExpression != null)     {         if(convertExpression.NodeType != ExpressionType.Convert)         {             throw new ArgumentException("Invalid property expression.", "exp");         }         body = convertExpression.Operand;     }     return ((MemberExpression)body).Member.Name; } 

Usage:

var x = new ObjectType(); // note that in this case we don't need to specify types of x and Property1 var propName1 = GetPropertyName(() => x.Property1); // assumes Property2 is an int property var propName2 = GetPropertyName<ObjectType, int>(y => y.Property2); // requires only object type var propName3 = GetPropertyName<ObjectType>(y => y.Property3); 

Update: fixed GetPropertyName<TObject>(Expression<Func<TObject, object>> exp) for properties returning value types.

Answer 2

class Foo
{
    public string Bar { get; set; }
}

class Program
{
    static void Main()
    {
        var result = Get<Foo, string>(x => x.Bar);
        Console.WriteLine(result);
    }

    static string Get<T, TResult>(Expression<Func<T, TResult>> expression)
    {
        var me = expression.Body as MemberExpression;
        if (me != null)
        {
            return me.Member.Name;
        }
        return null;
    }
}