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FileDialog.DefaultExt Property

Gets or sets a value that specifies the default extension string to use to filter the list of files that are displayed.

Namespace:  Microsoft.Win32
Assembly:  PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: Not mapped to an xmlns.

public string DefaultExt { get; set; }
<object DefaultExt="string" .../>

Property Value

Type: System.String
The default extension string. The default is Empty.

The extension string must contain the leading period. For example, set the DefaultExt property to ".txt" to select all text files.

By default, the AddExtension property attempts to determine the extension to filter the displayed file list from the Filter property. If the extension cannot be determined from the Filter property, DefaultExt will be used instead.

The following example shows how to create an OpenFileDialog that contains a default file name and extension type.

// Configure open file dialog box
Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
dlg.FileName = "Document"; // Default file name
dlg.DefaultExt = ".txt"; // Default file extension
dlg.Filter = "Text documents (.txt)|*.txt"; // Filter files by extension 

// Show open file dialog box
Nullable<bool> result = dlg.ShowDialog();

// Process open file dialog box results 
if (result == true)
{
    // Open document 
    string filename = dlg.FileName;
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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