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How to: Stretch a ToolStripTextBox to Fill the Remaining Width of a ToolStrip (Windows Forms)

When you set the Stretch property of a ToolStrip control to true, the control fills its container from end to end, and resizes when its container resizes. In this configuration, you may find it useful to stretch an item in the control, such as a ToolStripTextBox, to fill the available space and to resize when the control resizes. This stretching is useful, for example, if you want to achieve appearance and behavior similar to the address bar in Microsoft® Internet Explorer.


The following code example provides a class derived from ToolStripTextBox called ToolStripSpringTextBox. This class overrides the GetPreferredSize method to calculate the available width of the parent ToolStrip control after the combined width of all other items has been subtracted. This code example also provides a Form class and a Program class to demonstrate the new behavior.

using System;
using System.Drawing;
using System.Windows.Forms;

public class ToolStripSpringTextBox : ToolStripTextBox
    public override Size GetPreferredSize(Size constrainingSize)
        // Use the default size if the text box is on the overflow menu
        // or is on a vertical ToolStrip.
        if (IsOnOverflow || Owner.Orientation == Orientation.Vertical)
            return DefaultSize;

        // Declare a variable to store the total available width as 
        // it is calculated, starting with the display width of the 
        // owning ToolStrip.
        Int32 width = Owner.DisplayRectangle.Width;

        // Subtract the width of the overflow button if it is displayed. 
        if (Owner.OverflowButton.Visible)
            width = width - Owner.OverflowButton.Width -

        // Declare a variable to maintain a count of ToolStripSpringTextBox 
        // items currently displayed in the owning ToolStrip. 
        Int32 springBoxCount = 0;

        foreach (ToolStripItem item in Owner.Items)
            // Ignore items on the overflow menu.
            if (item.IsOnOverflow) continue;

            if (item is ToolStripSpringTextBox)
                // For ToolStripSpringTextBox items, increment the count and 
                // subtract the margin width from the total available width.
                width -= item.Margin.Horizontal;
                // For all other items, subtract the full width from the total
                // available width.
                width = width - item.Width - item.Margin.Horizontal;

        // If there are multiple ToolStripSpringTextBox items in the owning
        // ToolStrip, divide the total available width between them. 
        if (springBoxCount > 1) width /= springBoxCount;

        // If the available width is less than the default width, use the
        // default width, forcing one or more items onto the overflow menu.
        if (width < DefaultSize.Width) width = DefaultSize.Width;

        // Retrieve the preferred size from the base class, but change the
        // width to the calculated width. 
        Size size = base.GetPreferredSize(constrainingSize);
        size.Width = width;
        return size;

public class Form1 : Form
    public Form1()
        ToolStrip toolStrip1 = new ToolStrip();
        toolStrip1.Dock = DockStyle.Top;
        toolStrip1.Items.Add(new ToolStripLabel("Address"));
        toolStrip1.Items.Add(new ToolStripSpringTextBox());
        toolStrip1.Items.Add(new ToolStripButton("Go"));
        Text = "ToolStripSpringTextBox demo";

static class Program
    static void Main()
        Application.Run(new Form1());

Compiling the Code

This example requires:

  • References to the System, System.Drawing, and System.Windows.Forms assemblies.

See Also