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c# store function in list or call function by name

Posted on 2013-05-18
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Last Modified: 2013-05-18
I have a list box and when I click on it, I fire off a function corresponding to that item.

so if I click "Order History" then function OrderHistory is called.  I do this by adding strings to the listbox, then having a case statement and test the string and call a function.  I'd rather add a string and a function to some list and call it a better way.  It would save me typing

something like
List<string, function>functions;

functions.add("Order History", OrderHistory());

execute(string functionname)
functions...somehow call that function

This is basically a cheap rip off of a command pattern that I used.  this is just for one testing form and i want it to be easy.
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Question by:jackjohnson44
  • 3
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7 Comments
 
LVL 14

Assisted Solution

by:Vel Eous
Vel Eous earned 1000 total points
ID: 39177914
Perhaps something like the following (bit rough and ready):

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;

namespace Sandbox.wpf
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs args)
        {
            var selected = (sender as ListBox).SelectedItems;
            if (selected.Count > 0)
            {
                foreach (var item in selected)
                {
                    string functionToExecute = (item as ListBoxItem).Content.ToString();
                    Console.WriteLine(functionToExecute);
                    MethodInfo method = this.GetType().GetMethod(functionToExecute);
                    object result = method.Invoke(this, new object[] { "Hello World" });
                }
            }
        }

        public bool Function1(string str)
        {
            MessageBox.Show(str);
            return true;
        }

        public bool Function2(string str)
        {
            MessageBox.Show(str);
            return true;
        }
    }
}

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Author Comment

by:jackjohnson44
ID: 39177934
Thanks!  I am having an issue though.  For some reason, my GetMethod is always null.

        private void Calling()
        {
             //always null
            MethodInfo method = this.GetType().GetMethod("FunctionToCall");
            object result = method.Invoke(this, null);
        }
        private void FunctionToCall()
        {
            MessageBox.Show("It Works");
        }
0
 
LVL 14

Expert Comment

by:Vel Eous
ID: 39177937
The GetMethod function can only reflect on public methods.
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LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 1000 total points
ID: 39178002
The GetMethod function can only reflect on public methods.
I don't believe that's accurate.

I don't see the need for Reflection here. Just populate your list box with the delegates you want to invoke.

e.g.

using System;
using System.Windows.Forms;

namespace _28132404
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.listBox1.Items.Add(new ListItem() { DisplayValue = "Run Func1", FuncToInvoke = Func1 });
            this.listBox1.Items.Add(new ListItem() { DisplayValue = "Run Func2", FuncToInvoke = Func2 });
            this.listBox1.Items.Add(new ListItem() { DisplayValue = "Run Func3", FuncToInvoke = Func3 });
        }

        private void Func1()
        {
            MessageBox.Show("Hello World!");
        }

        private void Func2()
        {
            MessageBox.Show("Weather's nice today.");
        }

        private void Func3()
        {
            MessageBox.Show("Goodbye world!");
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (this.listBox1.SelectedItem != null)
            {
                ListItem item = this.listBox1.SelectedItem as ListItem;

                if (item != null)
                {
                    item.FuncToInvoke();
                }
            }
        }
    }

    public class ListItem
    {
        public string DisplayValue { get; set; }
        public Action FuncToInvoke { get; set; }

        public override string ToString()
        {
            return this.DisplayValue;
        }
    }
}

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LVL 14

Expert Comment

by:Vel Eous
ID: 39178012
I don't believe that's accurate.

You're correct, I completely forgot about and forgot to check its overloads.  Thanks for pointing that out.

http://msdn.microsoft.com/en-us/library/system.type.getmethod(v=vs.110).aspx
0
 

Author Comment

by:jackjohnson44
ID: 39178040
Thanks guys, one more question though.

How can i split up the step so that i create a list bind the listbox to it?

I don't want to:
this.listBox1.Items.Add(new ListItem() { DisplayValue = "Run Func1", FuncToInvoke = Func1 });
0
 

Author Comment

by:jackjohnson44
ID: 39178090
Thanks, I went with this:
        private Dictionary<string, Action> actions = new Dictionary<string, Action>();

            actions.Add("Log Me In", Login);

             actions[commandName].Invoke();
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