WPF SaveFileDialog DefaultExt ignored?

Question

var dlg = new SaveFileDialog();
dlg.FileName = "graph";
dlg.DefaultExt = ".bmp";
dlg.Filter = "PNG|*.png|DOT|*.dot|Windows Bitmap Format|*.bmp|GIF|*.gif|JPEG|*.jpg|PDF|*.pdf|Scalable Vector Graphics|*.svg|Tag Image File Format|*.tiff";

The extension always defaults to .png. It seems the DefaultExt is ignored if there is a Filter; then it just defaults to the first option in the list.

Is there a way to force it to actually respect the default ext?

Mendive

Answer 1

I'm a few years too late, but coincidentally, I found a solution to the problem while looking at the code from this question.

There he specified the extension without a .. I then looked into the microsoft documentation. In the example the DefaultExt was also specified without a ..

If DefaultExt is specified with a ., FileDialog will automatically choose the first extension of the filter.

DefaultExt should be set to the extension without a ..
Meaning that in your example dlg.DefaultExt = ".bmp"; you need to change ".bmp" to "bmp"...

Infest

Answer 2

You should set FilterIndex property instead of DefaultExt. If you still want to use DefaultExt, you can convert it to proper filter index manually:

public static void UseDefaultExtAsFilterIndex(FileDialog dialog)
{
    var ext = "*." + dialog.DefaultExt;
    var filter = dialog.Filter;
    var filters = filter.Split('|');
    for(int i = 1; i < filters.Length; i += 2)
    {
        if(filters[i] == ext)
        {
            dialog.FilterIndex = 1 + (i - 1) / 2;
            return;
        }
    }
}

var dlg = new SaveFileDialog();
dlg.FileName = "graph";
dlg.DefaultExt = ".bmp";
dlg.Filter = "PNG|*.png|DOT|*.dot|Windows Bitmap Format|*.bmp|GIF|*.gif|JPEG|*.jpg|PDF|*.pdf|Scalable Vector Graphics|*.svg|Tag Image File Format|*.tiff";
UseDefaultExtAsFilterIndex(dlg);
dlg.ShowDialog();

Lindner

Change the comparison to "Contains()" for multiple file types, e. g. "Excel (.xls;.xlsx)|*.xls;*.xlsx|". – Antirrhinum

Answer 3

DefaultExt is the extension that will be used if the user selects a file name with no extension (atleast that's my understanding from reading the description from MSDN).

When the user of your application specifies a file name without an extension, the FileDialog appends an extension to the file name.

You may have to make bmp the first item in the filter list.

Vernacularism

Answer 4

There is different explanations depending on API, but seem to work similarly; DefaultExt is used when the user selects a file name with no extension AND selected filter is a wildcard filter, like (*.*).

System.Windows.Forms.FileDialog.DefaultExt (MSDN):

When the user of your application specifies a file name without an extension, the FileDialog appends an extension to the file name. The extension that is used is determined by the Filter and DefaultExt properties. If a filter is selected in the FileDialog and the filter specifies an extension, then that extension is used. If the filter selected uses a wildcard in place of the extension, then the extension specified in the DefaultExt property is used.

Microsoft.Win32.FileDialog.DefaultExt (MSDN):

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.

Nobles