WinForms combobox with multiple columns (C#)?

Question

I am using currently the following code to populate a combobox:

combobox.DataSource = datatable;
combobox.DisplayMember = \"Auftragsnummer\";
combobox.ValueM         


        

Answer 1

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?

Answer 2

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

Multicolumn Combobox - Code Project

Answer 3

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

Answer 4

Here's the full solution in C# which I've converted from Visual basic: I've been using that for the past 8 years. Note the date format is for non-American users.

    using System;
    using System.ComponentModel;
    using System.Drawing;
    using System.Drawing.Drawing2D;
    using System.Data;
    using System.Windows.Forms;

   

     namespace MultiColumnCombcs
     {
        public partial class MultiColumnCombocs: ComboBox
        {
        // Hide some properties
        [Browsable(false)]
        public new bool IntegralHeight { get; set; }

        [Browsable(false)]
        public new DrawMode DrawMode { get; set; }

        [Browsable(false)]
        public new int DropDownHeight { get; set; }

        [Browsable(false)]
        public new ComboBoxStyle DropDownStyle { get; set; }

        [Browsable(false)]
        public new bool DoubleBuffered { get; set; }

        public Boolean paintHandled = false;
        public const int WM_PAINT = 0xF;
        public int intScreenMagnification = 125; // Screen Magnification = 125%
        // Dropdown
        private string _columnWidths;
        private string[] columnWidthsArray;

        // 'Combo Box
        private Color _buttonColor = Color.Gainsboro;
        private Color _borderColor = Color.Gainsboro;
        private readonly Color bgSelectedColor = Color.PaleGreen; 
        private readonly Color textselectedcolor = Color.Red;
        private readonly Color bgColor = Color.White;
        private readonly Color lineColor = Color.White;
       
        private Brush backgroundBrush = new SolidBrush(SystemColors.ControlText);
        private Brush arrowBrush = new SolidBrush(Color.Black);
        private Brush ButtonBrush = new SolidBrush(Color.Gainsboro);

        //Properties
        [Browsable(true)]
        public Color ButtonColor
        {
            get
            {
                return _buttonColor;
            }
            set
            {
                _buttonColor = value;
                ButtonBrush = new SolidBrush(this.ButtonColor);
                this.Invalidate();
            }
        }

        [Browsable(true)]
        public Color BorderColor
        {
            get
            {
                return _borderColor;
            }
            set
            {
                _borderColor = value;
                this.Invalidate();
            }
        }
        //Column Widths to be set in Properties Window as string containing width of each column in Pixels, 
        // delimited by ';' eg 15;45;40;100,50;40 for six columns

        [Browsable(true)]
        public string ColumnWidths 
        {
            get
            {
            if (string.IsNullOrEmpty(_columnWidths))
                {
                    _columnWidths = "15";  //default value
                }

                return _columnWidths;
            }
            set
            {
                _columnWidths = value;
                // split Column Widths string into Array of substrings delimitted by ';' character
                columnWidthsArray = _columnWidths.Split(System.Convert.ToChar(";")); 
                int w = 0;
                foreach (string str in columnWidthsArray)
                    w += System.Convert.ToInt32(System.Convert.ToInt32(str) * intScreenMagnification / 100);// ******
                DropDownWidth = (w + 20);
            }
        }
        // Constructor stuff
        public MultiColumnCombocs() : base()
        {
            base.IntegralHeight = false;
            base.DrawMode = DrawMode.OwnerDrawFixed;
            base.DropDownStyle = ComboBoxStyle.DropDown;
            MaxDropDownItems = 12;
            // Minimise flicker in painted control
            SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
        }
        protected override void WndProc(ref Message m)  // Listen for operating system messages
        {   
            base.WndProc(ref m);  /*Inheriting controls should call the base class's WndProc(Message) method
                                    to process any messages that they do not handle.*/
            switch (m.Msg)
            {
                case WM_PAINT:
                    // Draw Combobox and dropdown arrow
                    Graphics g = this.CreateGraphics();
                    // Background - Only the borders will show up because the edit box will be overlayed
                    try
                    {
                        backgroundBrush = new SolidBrush(Color.White);
                        g.FillRectangle(backgroundBrush, 0, 0, Size.Width, Size.Height);
                        // Border
                        Rectangle rectangle = new Rectangle();
                        Pen pen = new Pen(BorderColor, 2);
                        rectangle.Size = new Size(Width - 2, Height);
                        g.DrawRectangle(pen, rectangle);
                        
                        // Background of the dropdown button
                        ButtonBrush = new SolidBrush(ButtonColor);
                        Rectangle rect = new Rectangle(Width - 15, 0, 15, Height);
                        g.FillRectangle(ButtonBrush, rect);

                        // Create the path for the arrow
                        g.SmoothingMode = SmoothingMode.AntiAlias;

                        GraphicsPath pth = new GraphicsPath();
                        PointF TopLeft = new PointF(Width - 12, System.Convert.ToSingle((Height - 5) / 2));
                        PointF TopRight = new PointF(Width - 5, System.Convert.ToSingle((Height - 5) / 2));
                        PointF Bottom = new PointF(Width - 8, System.Convert.ToSingle((Height + 4) / 2));
                        pth.AddLine(TopLeft, TopRight);
                        pth.AddLine(TopRight, Bottom);

                        // Determine the arrow and button's color.
                        arrowBrush = new SolidBrush(Color.Black);

                        if (this.DroppedDown)
                        {
                            arrowBrush = new SolidBrush(Color.Red);
                            ButtonBrush = new SolidBrush(Color.PaleGreen);
                        }
                        // Draw the arrow
                        g.FillRectangle(ButtonBrush, rect);
                        g.FillPath(arrowBrush, pth);

                        pen.Dispose();
                        pth.Dispose();

                    }
                    finally
                    {
                        // Cleanup
                        g.Dispose();
                        arrowBrush.Dispose();
                        backgroundBrush.Dispose();
                    }
                    break;
                   
               default:
                  {
                    break;
                  }
            }
           
        }
        protected override void OnDrawItem(System.Windows.Forms.DrawItemEventArgs e)
        {
            // Draw Dropdown with Multicolumns
            Cursor = Cursors.Arrow;
            DataRowView row = (DataRowView)base.Items[e.Index];

            int newpos = e.Bounds.X;
            int endpos = e.Bounds.X;
            int intColumnIndex = 0;

            // Draw the current item text based on the current Font and the custom brush settings
            foreach (string str in columnWidthsArray)
            {
                // paint each column, "intColumnIndex" is local integer
                string strColWidth = columnWidthsArray[intColumnIndex];
                int ColLength = System.Convert.ToInt32(strColWidth);
                // Adjust ColLength
                ColLength = System.Convert.ToInt32(ColLength * intScreenMagnification / 100); // ******
                endpos += ColLength;

                string strColumnText = row[intColumnIndex].ToString();

                if (IsDate(strColumnText))  //Format Date as 'dd-MM-yy' (not avail as 'ToString("Format")'
                {
                    strColumnText = strColumnText.Replace("/", "-");
                    string strSaveColumn = strColumnText;
                    strColumnText = strSaveColumn.Substring(0, 6) + strSaveColumn.Substring(8, 2);
                    ColLength = 40;
                }

                // Paint Text
                if (ColLength > 0)
                {
                    RectangleF r = new RectangleF(newpos + 1, e.Bounds.Y, endpos - 1, e.Bounds.Height);
                    // Colours of normal row and text

                    //   Colours of normal row and text
                    SolidBrush textBrush = new SolidBrush(Color.Black);
                    SolidBrush backbrush = new SolidBrush(Color.White);
                    StringFormat strFormat = new StringFormat();
                    try 
                    {
                        // Colours of selected row and text
                        if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
                        {
                            textBrush.Color = textselectedcolor; // Red
                            backbrush.Color = bgSelectedColor; // Pale Green
                        }
                        e.Graphics.FillRectangle(backbrush, r);

                        strFormat.Trimming = StringTrimming.Character;
                        e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
                        e.Graphics.DrawString(strColumnText, e.Font, textBrush, r, strFormat);
                        e.Graphics.SmoothingMode = SmoothingMode.None;
                    }
                    finally
                    { 
                        backbrush.Dispose();
                        strFormat.Dispose();
                        textBrush.Dispose();
                    }

                    //Separate columns with white border
                    if (intColumnIndex > 0 && intColumnIndex <= (columnWidthsArray.Length))
                    {
                        e.Graphics.DrawLine(new Pen(Color.White), endpos, e.Bounds.Y, endpos, ItemHeight * MaxDropDownItems);
                    }
                    newpos = endpos;
                    intColumnIndex++;
                } // end if
            }// end for
        } //end sub

    private bool IsDate(string strColumnText)
    {
        DateTime dateValue;

        if (DateTime.TryParse(strColumnText, out dateValue))
        {
            return true;
        }
        else
        {
            return false;
        }
    } // end sub

        protected override void OnMouseWheel(MouseEventArgs e)
        {
            // Overrides Sub of same name in parent class
            HandledMouseEventArgs MWheel = (HandledMouseEventArgs)e;
            // HandledMouseEventArgs prevents event being sent to parent container
            if (!this.DroppedDown)
            {
                MWheel.Handled = true;
            }
        }

        protected override void OnKeyDown(KeyEventArgs e)
        {
            base.OnKeyDown(e);
            if (!this.DroppedDown & e.KeyCode == Keys.Down)
                this.DroppedDown = true;
            else if (e.KeyCode == Keys.Escape)
            {
                this.SelectedIndex = -1;
                this.Text = "";
            }
        }
    }
}

Answer 5

easy and quick! look at this...

combobox.Datasource = 
entities.tableName.Select(a => a.Coulmn1 + " " + a.Coulmn2).ToList();

Answer 6

Quick solution
Datatables should be partical classes as far as I remember

1. Create a 2nd file for your datatable MyDataTable.custom.cs
2. Add a string property in the partial datatable class called "DisplayProperty"
3. In that property return a string.format("{0} {1} {2}", Auftragsnummer, Kunde, Beschreibung);
4. Bind your Datamember to your DisplayProperty