Question

I’m setting up a simple helper class to hold some data from a file I’m parsing. The names of the properties match the names of values that I expect to find in the file. I’d like to add a method called AddPropertyValue to my class so that I can assign a value to a property without explicitly calling it by name.

The method would look like this:

//C#
public void AddPropertyValue(string propertyName, string propertyValue) {
   //code to assign the property value based on propertyName
}

---

'VB.NET'
Public Sub AddPropertyValue(ByVal propertyName As String, _
                            ByVal propertyValue As String)
    'code to assign the property value based on propertyName '
End Sub

The implementation might look like this:

C#/VB.NET

MyHelperClass.AddPropertyValue("LocationID","5")

Is this possible without having to test for each individual property name against the supplied propertyName?

Answer 1

You can do this with reflection, by calling Type.GetProperty and then PropertyInfo.SetValue. You’ll need to do appropriate error handling to check for the property not actually being present though.

Here’s a sample:

using System;
using System.Reflection;

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

    public void AddPropertyValue(string name, string value)
    {
        PropertyInfo property = typeof(Test).GetProperty(name);
        if (property == null)
        {
            throw new ArgumentException("No such property!");
        }
        // More error checking here, around indexer parameters, property type,
        // whether it's read-only etc
        property.SetValue(this, value, null);
    }

    static void Main()
    {
        Test t = new Test();
        t.AddPropertyValue("Foo", "hello");
        t.AddPropertyValue("Bar", "world");

        Console.WriteLine("{0} {1}", t.Foo, t.Bar);
    }
}

If you need to do this a lot, it can become quite a pain in terms of performance. There are tricks around delegates which can make it a lot faster, but it’s worth getting it working first.