get filepath in database?

hi any help how can i get the file path i got an error like Object reference not set to an instance of an object. heres ny code
FileUpload f_docs = new FileUpload();
// Label f_docs = new Label();
string filename = @"C:\OFW2012\images\documents\" + sdr_docs1.GetValue(sdr_docs1.GetOrdinal("filename")).ToString();
f_docs.PostedFile.SaveAs(filename);  // eror here
FileUploadContainer.Controls.Add(f_docs);

but my path was correct.. idont know why i got this error.. thanks
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