[Description] Opens the file if it exists and seeks to the end of the file, or creates a new file. This operation requires FileIOPermissionAccess.Append permission. FileMode.Append can be used only in conjunction with FileAccess.Write. Trying to seek to a position before the end of the file throws an IOException exception, and any attempt to read fails and throws an NotSupportedException exception. [Member name] 
Append
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