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CheckBox.ThreeState Property

Gets or sets a value indicating whether the CheckBox will allow three check states rather than two.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public bool ThreeState { get; set; }

Property Value

Type: System.Boolean
true if the CheckBox is able to display three check states; otherwise, false. The default value is false.

If the ThreeState property is set to false, the CheckState property value can only be set to the Indeterminate value of System.Windows.Forms.CheckState in code and not by user interaction.

The following code example displays the values of three properties in a label. The ThreeState property alternates between true and false with alternating clicks of the control and the CheckAlign alternates between the MiddleRight and MiddleLeft values of System.Drawing.ContentAlignment. This example shows how the property values change as the ThreeState property changes and the control is checked. This code requires that a CheckBox, Label and Button have all been instantiated on a form and that the label is large enough to display three lines of text, as well as a reference to the System.Drawing namespace. This code should be called in the Click event handler of the control.

private void AdjustMyCheckBoxProperties()
 {
    // Change the ThreeState and CheckAlign properties on every other click. 
    if (!checkBox1.ThreeState)
    {
       checkBox1.ThreeState = true;
       checkBox1.CheckAlign = ContentAlignment.MiddleRight;
    }
    else
    {
       checkBox1.ThreeState = false;
       checkBox1.CheckAlign = ContentAlignment.MiddleLeft;
    }

    // Concatenate the property values together on three lines.
    label1.Text = "ThreeState: " + checkBox1.ThreeState.ToString() + "\n" +
                  "Checked: " + checkBox1.Checked.ToString() + "\n" +
                  "CheckState: " + checkBox1.CheckState.ToString(); 
 }
 

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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