ComboBox自定义显示

Question

I have created a Custom Combo Box where-in I have been able to Display Multi-Column items along with image when ComboBox is dropped down. Now the problem I am facing is when an item is selected, i need to display the item exactly as it was displayed in dropdown list ie . So which event I should do it in? Or How can I accomplish this?

So far I have this

public partial class XComboBox : ComboBox
{
    private Int32 ColumnGap = 10;
    private Int32 firstColumnWidth;
    private Int32 secondColumnWidth;

    public XComboBox()
    {
        DrawMode = DrawMode.OwnerDrawFixed;
        firstColumnWidth = DropDownWidth / 2;
        secondColumnWidth = DropDownWidth / 2;
        AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.ListItems;

    }

    public Boolean MultiColumn
    {
        get;
        set;
    }

    public String ColumnWidths
    {
        get
        {
            return String.Concat(firstColumnWidth.ToString(), ";", secondColumnWidth.ToString());
        }
        set
        {
            if (Regex.Match(value, "^[0-9]+;[0-9]+$").Success)
            {
                String[] widths = value.Split(';');
                firstColumnWidth = Int32.Parse(widths[0]);
                secondColumnWidth = Int32.Parse(widths[1]);
                DropDownWidth = (firstColumnWidth + secondColumnWidth + ColumnGap) > Width ? (firstColumnWidth + secondColumnWidth + ColumnGap) : Width;
            }
            else
            {
                throw new ArgumentException("Invalid argument specified. Value of ColumnWidths property should be in \"[0-9];[0-9]\" format");
            }
        }
    }

    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        XComboItem item = (XComboItem)Items[e.Index];
        ColumnGap = firstColumnWidth == 0 ? 0 : ColumnGap;

        e.DrawBackground();
        e.DrawFocusRectangle();

        string first = item.DisplayName;
        string second = item.Description;

        if (MultiColumn)
        {
            while (TextRenderer.MeasureText(first, e.Font).Width > firstColumnWidth)
            {
                first = first.Substring(0, first.Length - 1);
            }

            e.Graphics.DrawString(first, e.Font, new SolidBrush(e.ForeColor), e.Bounds.Left, e.Bounds.Top);
            e.Graphics.DrawString(second, e.Font, new SolidBrush(e.ForeColor), e.Bounds.Left + firstColumnWidth + ColumnGap, e.Bounds.Top);
        }
        else
        {
            e.Graphics.DrawString(second, e.Font, new SolidBrush(e.ForeColor), e.Bounds.Left, e.Bounds.Top);
        }
    }

    protected override void OnMeasureItem(MeasureItemEventArgs e)
    {
        base.OnMeasureItem(e);
    }

    protected override void OnSelectedValueChanged(EventArgs e)
    {
        base.OnSelectedValueChanged(e);
    }
}   

public class XComboItem
{
    public Int32 ItemId { get; set; }
    public String DisplayName { get; set; }
    public Object Value { get; set; }
    public String Description { get; set; }

    public XComboItem()
    {
        DisplayName = String.Empty;
        Description = String.Empty;
        DisplayText = String.Empty;
    }

    internal String DisplayText
    {
        get;
        set;
    }

    public override string ToString()
    {
        return DisplayName;            
    }
}

Answer 1

I assume you don't expect the user to type - given the format. For this, you need to set DropDownStyle == DropDownList . .. and your current code should work just fine.

OnDrawItem is called for both the drop down and the top edit/text box portion.

As explained in: https://stackoverflow.com/a/5111692/631687 , you can differentiate which is being rendered.