NGWS SDK Documentation  

This is preliminary documentation and subject to change.
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This key is already associated with an element of this collection (Error 457)

A key is a string specified in the Add method that uniquely identifies a specific member of a collection. This error has the following cause and solution:

For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).

See Also

Add Method