ComboBox.SelectedValue returns null

[Fallen]

In the code below, m_list.SelectedValue returns null in
MainForm.valueChanged regardless of which value is selected. Is this
expected behaviour? However, SelectedItem *does* return the correct
value.

[code]
using System;
using System.Windows.Forms;

class Attr { // a simple name value class
string m_name;
string m_value;
public Attr(string name, string value){ m_name = name; m_value
=
value; }
public string Name { get { return m_name; } }
public string Value { get { return m_value; } }

}

public class MainForm : Form {
public static void Main(string[] args){
Application.Run(new MainForm());
}

ComboBox m_list;

public MainForm(){
m_list = new ComboBox();
Controls.Add(m_list);
m_list.DisplayMember = "Name";
m_list.ValueMember = "Value";

m_list.Items.Add(new Attr("one", "1"));
m_list.Items.Add(new Attr("two", "2"));
m_list.Items.Add(new Attr("three", "3"));

m_list.SelectedValueChanged += new
EventHandler(valueChanged);
}

public void valueChanged(object sender, EventArgs args){
if(m_list.SelectedIndex != -1)
Text = m_list.SelectedValue.ToString();
}

}
[/code]

[Bob Powell [MVP]]

Works fine when data binding is used instead of list initialisation...

public class Form1 : Form

{

BindingList<foo> bl = new BindingList<foo>();

public Form1()

{

InitializeComponent();

bl.AllowNew = true;

bl.Add(new foo("egg", 1));

bl.Add(new foo("sock", 2));

bl.Add(new foo("bottle", 3));

this.comboBox1.DataSource = bl;

this.comboBox1.SelectedIndex = 0;

this.comboBox1.SelectedValueChanged += new
EventHandler(comboBox1_SelectedValueChanged);

}

void comboBox1_SelectedValueChanged(object sender, EventArgs e)

{

this.Text = this.comboBox1.SelectedValue.ToString();

}

/// <summary>

/// Required designer variable.

/// </summary>

private System.ComponentModel.IContainer components = null;

/// <summary>

/// Clean up any resources being used.

/// </summary>

/// <param name="disposing">true if managed resources should be disposed;
otherwise, false.</param>

protected override void Dispose(bool disposing)

{

if (disposing && (components != null))

{

components.Dispose();

}

base.Dispose(disposing);

}

#region Windows Form Designer generated code

/// <summary>

/// Required method for Designer support - do not modify

/// the contents of this method with the code editor.

/// </summary>

private void InitializeComponent()

{

this.comboBox1 = new System.Windows.Forms.ComboBox();

this.SuspendLayout();

//

// comboBox1

//

this.comboBox1.FormattingEnabled = true;

this.comboBox1.Location = new System.Drawing.Point(34, 43);

this.comboBox1.Name = "comboBox1";

this.comboBox1.Size = new System.Drawing.Size(121, 21);

this.comboBox1.TabIndex = 0;

//

// Form1

//

this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);

this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;

this.ClientSize = new System.Drawing.Size(284, 264);

this.Controls.Add(this.comboBox1);

this.Name = "Form1";

this.Text = "Form1";

this.ResumeLayout(false);

}

#endregion

private System.Windows.Forms.ComboBox comboBox1;

}

class foo

{

public foo(string n, int v)

{

name = n;

value = v;

}

string name;

public string Name

{

get { return name; }

set { name = value; }

}

int value;

public int Value

{

get { return this.value; }

set { this.value = value; }

}

public override string ToString()

{

return name +":"+ value.ToString();

}

}

--
--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

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"Fallen" <sw.tej...@gmail.com> wrote in message
news:1179717022.8...@36g2000prm.googlegroups.com...

[Fallen]

Yes data binding does work. But it is strange that the DisplayMember
is respected in both cases but the ValueMember is respected only in
the data binding case.

Thanks, Bob.

On May 21, 2:22 pm, "Bob Powell [MVP]" <b...@spamkillerbobpowell.net>
wrote:

> Works fine when data binding is used instead of list initialisation...
>

regards,
Fallen