Name 'DiffGram' is not declared.

[Guoqi Zheng]

Dear sir,

I am very new to asp.net. I often meet a problem of name 'xxx' is not declared. can some one tell me what is the problem? For example, my following code gives me an error of "Name 'DiffGram' is not declared." what should I do?

Dim myFileStream As New System.IO.FileStream _
(filename, System.IO.FileMode.Create)
' Write to the file with the WriteXml method.
objDataSet.WriteXml(myFileStream, DiffGram)
myFileStream.Close()

Thanks a lot!!!