WinForms combobox with multiple columns (C#)?

You can't have multiple columns. Though you can have concatenation of multiple fields as Display Member

Check out: How do I bind a Combo so the displaymember is concat of 2 fields of source datatable?

There's an article on MSDN describing how a Multicolumn ComboBox can be created.

How to create a multiple-column drop-down list for a combo box in Windows Forms

http://support.microsoft.com/kb/982498

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Source code from the download for VB from the above Microsoft Link, that can be easily adapted to work with a ListBox as well as a ComboBox:

'************************************* Module Header **************************************'
' Module Name:  MainForm.vb
' Project:      VBWinFormMultipleColumnComboBox
' Copyright (c) Microsoft Corporation.
' 
' 
' This sample demonstrates how to display multiple columns of data in the dropdown of a ComboBox.
' 
' This source is subject to the Microsoft Public License.
' See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
' All other rights reserved.
' 
' THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
' EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
' WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
'******************************************************************************************'

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports System.Drawing.Drawing2D

Public Class MainForm

    Private Sub MainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim dtTest As DataTable = New DataTable()
        dtTest.Columns.Add("ID", GetType(Integer))
        dtTest.Columns.Add("Name", GetType(String))

        dtTest.Rows.Add(1, "John")
        dtTest.Rows.Add(2, "Amy")
        dtTest.Rows.Add(3, "Tony")
        dtTest.Rows.Add(4, "Bruce")
        dtTest.Rows.Add(5, "Allen")

        ' Bind the ComboBox to the DataTable
        Me.comboBox1.DataSource = dtTest
        Me.comboBox1.DisplayMember = "Name"
        Me.comboBox1.ValueMember = "ID"

        ' Enable the owner draw on the ComboBox.
        Me.comboBox1.DrawMode = DrawMode.OwnerDrawFixed
        ' Handle the DrawItem event to draw the items.
    End Sub

    Private Sub comboBox1_DrawItem(ByVal sender As System.Object, _
                                   ByVal e As System.Windows.Forms.DrawItemEventArgs) _
                                   Handles comboBox1.DrawItem
        ' Draw the default background
        e.DrawBackground()

        ' The ComboBox is bound to a DataTable,
        ' so the items are DataRowView objects.
        Dim drv As DataRowView = CType(comboBox1.Items(e.Index), DataRowView)

        ' Retrieve the value of each column.
        Dim id As Integer = drv("ID").ToString()
        Dim name As String = drv("Name").ToString()

        ' Get the bounds for the first column
        Dim r1 As Rectangle = e.Bounds
        r1.Width = r1.Width / 2

        ' Draw the text on the first column
        Using sb As SolidBrush = New SolidBrush(e.ForeColor)
            e.Graphics.DrawString(id, e.Font, sb, r1)
        End Using

        ' Draw a line to isolate the columns 
        Using p As Pen = New Pen(Color.Black)
            e.Graphics.DrawLine(p, r1.Right, 0, r1.Right, r1.Bottom)
        End Using

        ' Get the bounds for the second column
        Dim r2 As Rectangle = e.Bounds
        r2.X = e.Bounds.Width / 2
        r2.Width = r2.Width / 2

        ' Draw the text on the second column
        Using sb As SolidBrush = New SolidBrush(e.ForeColor)
            e.Graphics.DrawString(name, e.Font, sb, r2)
        End Using
    End Sub
End Class

You can add to your dataset a dummy column (Description) and use that as DisplayMember in the combo box databinding.

SELECT Users.*, Surname+' '+Name+' - '+UserRole AS Description FROM Users

ComboBox.DataBindings.Add(new Binding("SelectedValue", bs, "ID"));
ComboBox.DataSource = ds.Tables["Users"];
ComboBox.DisplayMember = "Description";
ComboBox.ValueMember = "ID";

Simple and works.

It's not available out-of-the-box in .NET (be it Windows forms or asp.net's dropdownlist) CHeck out this code project item for reference on how to build your own. (there are loads more though).

Code Project