CODEWITHSUNDEEP
c#forms
ItinerantEngineer
ItinerantEngineer

Reputation: 255

use variable name to access sub object

I have an object XMLLog that is retrieved from a database. A form allows a user to edit fields in the object, but because of convoluted reasons, I can't return the modified object, I'm returning a list of Keys in a Post.

I would like to do the following:

//get XMLLog from the database

foreach (var key in Request.Form.AllKeys)
{
    XMLLog.key = Request.Form[key];
}

//write XMLLog back to the Database

Is there any way to accomplish that without a giant case statement to test for each possible key?

Upvotes: 1

Views: 148

Answers (2)

Ran
Ran

Reputation: 6159

You can do this using reflection, but it would be very slow. Here's a small program that demonstrates the principal (you can compile and run it):

using System;
using System.Collections.Generic;
using System.Reflection;

class Program
{
    static void Main(string[] args)
    {
        var log = new XmlLog();
        var values = new Dictionary<string, string> { { "Hello", "1" }, { "World", "2" } };

        foreach (var methodInfo in typeof(XmlLog).GetProperties(BindingFlags.Instance | BindingFlags.Public))
        {
            methodInfo.SetValue(log, values[methodInfo.Name]);
        }

        Console.WriteLine(log.Hello);
        Console.WriteLine(log.World);
    }

    class XmlLog
    {
        public string Hello { get; set; }
        public string World { get; set; }
    }
}

This can be done faster by using code generation. You have several options like:

  1. Use Reflection over the XmlLog type and generate C# code that will be compiled along with your application.
  2. Use Reflection to build an Expression that sets XmlLog's properties, and then compile it into a Func or Action in runtime.

Upvotes: 3

Joe Enos
Joe Enos

Reputation: 40413

Reflection is how you would do this:

foreach (var key in Request.Form.AllKeys)
{
    var prop = typeof(XMLLog).GetProperty(key);
    prop.SetValue(myXmlLog, Request.Form[key], null);
}

This assumes a very simple structure with all strings - you may need to add validation, conversion, etc., depending on the data types and complexity of your XMLLog class.

This is not a great solution either. Ideally, you'd let the framework handle mapping form posts to an object, like with MVC. If you describe your environment a little more, maybe we can get a better answer.

Upvotes: 1

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