ValidationSummary.ShowMessageBox Property

This property can be used in addition to the ShowSummary property to control where the validation summary is displayed. If this property and EnableClientScript are both set to true, the validation summary is displayed in a message box. If EnableClientScript is set to false, this property has no effect.

Note
If both the ShowMessageBox and ShowSummary properties are set to true, the validation summary is displayed in both a message box and on the Web page.

The following code example demonstrates how to use the ShowMessageBox and ShowSummary properties to specify that the validation summary is displayed only in a message box.

<asp:ValidationSummary 
     id="valSum" 
     DisplayMode="BulletList"
     ShowMessageBox="true"
     ShowSummary="false" 
     HeaderText="You must enter a value in the following fields:"
     Font-Names="verdana" 
     Font-Size="12"
     runat="server"/>
   

.NET Framework

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.

Reference