Shows a dialog where the user can select a file from a directory. The returned string is a complete path and file name. If the cancel buttun is pressed then a null string is returned.
Parameter 
 | Description 
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DefName$  
 | Set the initial File Name in the to this string value. If this is omitted then *.DefExt$ is used.  
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DefExt$ 
 | Initially show files whose extension matches this string value. (Multiple extensions can be specified by using ";" as the separator.) If this is omitted then * is used.  
 | 
DefDir$  
 | This string value is the initial directory. If this is omitted then the current directory is used.  
 | 
Title$ 
 | This string value is the title of the dialog. If this is omitted then ''Open" is used.  
 | 
Option  
 | This numeric value determines the file selection options. If this is omitted then zero is used. See table below.  
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