IApplication.OpenDocument Method

Opens a document in this application.

[Visual Basic 6.0]
Sub OpenDocument(
    [ByVal path As String] _
) As Empty

[Visual Basic .NET]
Public Sub OpenDocument ( _
    [ByVal path As String] _
)

[C#]
public void OpenDocument (
    string path
);

[C#]

Optional Values

path To indicate that this parameter is undefined, pass in Type.Missing.

Available with ArcGIS Desktop.

Path is a string representing the path and filename of the document to be opened. [Optional]

If no Path is specified, the Open dialog is displayed.

Note, this method does not work in ArcCatalog.

EDN: ESRI Developer Network