Lieven Cardoen Lieven Cardoen - 8 days ago 5
C# Question

.NET Reflection set private property

If you have a property defined like this:

private DateTime modifiedOn;
public DateTime ModifiedOn
{
get { return modifiedOn; }
}


How do you set it to a certain value with Reflection?

I've tried both:

dto.GetType().GetProperty("ModifiedOn").SetValue(dto, modifiedOn, null);


and

dto.GetType().GetProperty("modifiedOn").SetValue(dto, modifiedOn, null);


but without any success. Sorry if this is a stupid question but it's the first time I'm using Reflection with C#.NET.

Answer

That has no setter; you'd need:

public DateTime ModifiedOn
{
    get { return modifiedOn; }
    private set {modifiedOn = value;}
}

(you might have to use BindingFlags - I'll try in a moment)

Without a setter, you'd have to rely on patterns / field names (which is brittle), or parse the IL (very hard).

The following works fine:

using System;
class Test {
    private DateTime modifiedOn;
    public DateTime ModifiedOn {     
        get { return modifiedOn; }
        private set { modifiedOn = value; }
    }
}
static class Program {
    static void Main() {
        Test p = new Test();
        typeof(Test).GetProperty("ModifiedOn").SetValue(
            p, DateTime.Today, null);
        Console.WriteLine(p.ModifiedOn);
    }
}

It also works with an auto-implemented property:

public DateTime ModifiedOn { get; private set; }

(where relying on the field-name would break horribly)

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