Reflection: Getting property name from property itself

[GazzaJ]

If I get a list of properties using GetProperties() how do I get the propertyInfo of the property I'm interested in without specifying a string to identify it.

[Judah Gabriel Himango]

You can do this using lambda expressions in C# 3. See http://themechanicalbride.blogspot.com/2007/03/symbols-on-steroids-in-c.html[^] for more info.

using System.Linq.Expressions;
public static class SymbolExtensions
{
    public static string GetPropertySymbol<T, R>(this T target, Expression<Func<T, R>> expression)
    {
        return ((MemberExpression)(((LambdaExpression)(expression)).Body)).Member.Name;
    }
}

You can then call it like this:

string propertyName = myObject.GetPropertySymbol(o => o.MyTestProperty);
myGrid.AddColumn(new ColumnDefn(propertyName, "", false, true));

Using this technique, you can get the name of a property or method without using strings at all. This can be beneficial in unit testing, INotifyPropertyChanged implementations, and other scenarios where hard-coding a string is a bad option.

Tech, life, family, faith: Give me a visit. I'm currently blogging about: What this world needs... (Video) The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

[GazzaJ]

That looks like what I want but I am stuck on .NET v2!

[Judah Gabriel Himango]

Stuck in 2.0 land, eh? The one possible way to do this without a string is from within the property or method itself:

string nameOfTheProperty;
...

public string MyProperty
{
   get
   {
       nameOfTheProperty = MethodInfo.GetCurrentMethod().Name;
   }
}

This has the obvious downside of having to invoke the property in order to get its name. Another possibility that works only with methods (it doesn't work with properties) is by using delegates:

MethodInvoker dummyDelegate = MyFunction;
string nameOfTheMethod = dummyDelegate.Method.Name;

...

void MyFunction()
{
}

Tech, life, family, faith: Give me a visit. I'm currently blogging about: What this world needs... (Video) The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

[S Senthil Kumar]

Thanks for the link. That was a really neat trick, must be the most creative use of ExpressionTrees I've found so far (besides their intended purpose).

Regards Senthil [MVP - Visual C#] _____________________________ My Blog | My Articles | My Flickr | WinMacro

[DavidNohejl]

Judah Himango wrote:

Another possibility that works only with methods (it doesn't work with properties) is by using delegates

I thought I had an idea but "cannot explicitly call operator or accessor" Damn.

---

[My Blog]
"Visual studio desperately needs some performance improvements. It is sometimes almost as slow as eclipse." - Rüdiger Klaehn
"Real men use mspaint for writing code and notepad for designing graphics." - Anna-Jayne Metcalfe

[PIEBALDconsult]

GetProperties() returns the PropertyInfo

[PIEBALDconsult]

Don't send in the name of the property, send in the PropertyInfo instead. typeof(myObject).GetProperty("TestPropertyName")

namespace Template
{
public class X
{
public string
Name
{
get
{
return ( "Malcolm" ) ;
}
}
}

public partial class Template
{
    private static void
    DisplayPropertyNameAndType
    (
        **System.Reflection.PropertyInfo Prop**
    )
    {
        System.Console.WriteLine
        (
            "{0} is {1}"
        ,
            **Prop.Name**
        ,
            **Prop.PropertyType**
        ) ;

        return ;
    }

    \[System.STAThreadAttribute()\]
    public static int
    Main
    (
        string\[\] args
    )
    {
        int result = 0 ;

        try
        {
            DisplayPropertyNameAndType ( **typeof(X).GetProperty ( "Name" )** ) ;
        }
        catch ( System.Exception err )
        {
            System.Console.Write ( err.Message ) ;
        }

        return ( result ) ;
    }
}

}

The PropertyInfo can also provide the type to which it belongs: .ReflectedType

modified on Monday, January 14, 2008 3:05:00 PM

[GazzaJ]

Thanks for all the help. I'm still not sure this is what I want. I don't want any hardcoded literal strings. In the code above I still have to use the string "Name" to get the information. I have an object myObject which has a property TestProperty ie myObject.TestProperty. Using only this I want to get a string of the property name e.g. SomeCode(myObject.TestProperty) returns "TestProperty"

[DaveyM69]

Have a look at the thread that this[^] message is in. Ed helped me enormously doing remarkable stuff with properties/reflection and more here - it might get you going in the direction you're looking for.

[PIEBALDconsult]

myObject.TestProperty results in only the value of the instance's property. myObject.GetType().GetProperty("TestProperty") should get you the property, but lose the instance. I think I need to go back and read this thread from the beginning again to see what I may have missed.

[PIEBALDconsult]

Yeah I still don't think it can be done without either myval.GetType().GetProperty("Name") or typeof(mytyp).GetProperty("Name") But, consider this... Write a custom Attribute and use it to decorate fields in the classes you want to use with your grid (assuming you only want to support classes you write). Then just pass the new type into your grid.

public class GridAttribute : Attribute {}

public class MyClass
{
[GridAttribute()]
public int SomeProperty ...
}

Grid grid = new Grid(typeof(MyClass)) ;
--or, better--
Grid grid = new Grid<myclass>() ; -- Fixed brackets

Then in the constructor for Grid: enumerate the fields of typeof(T) (MyClass) , enumerate the CustomAttributes of each, add each that has the attribute. P.S. This past week I was playing with passing an enum into a generic class that will investigate its fields looking for a CustomAttribute.

[NassosReyzidis]

Hi there, I have an idea that i saw first in the WPF implementation, you can put some public static const variables in your object implementation so that you can call the appropriate property: public class MyObject { public static const string refTestPropertyName = "TestPropertyName"; private string _TestPropertyName; public string TestPropertyName { get{return _TestPropertyName;} set{_TestPropertyName=value;} } .... } now in your code: MyObject myObject = new MyObject(); myGrid.AddColumn(new ColumnDefn(myObject.refTestPropertyName , "", false, true)); Hope that helped Nassos

"Success is the ability to go from one failure to another with no loss of enthusiasm." Winston Churchill "Quality means doing it right when no one is looking." Henry Ford