c# - Cannot implicitly convert type System.data.datatable to Microsoft.Office.Interop.Excel -

 public datatable populatevendorgridview()         {              dataset ds = new dataset();             ds = (dataset)session["vendorinvoiceid"];              return ds.tables[0]; //getting error here         } 

a datatable type exists in both namespaces:

microsoft.office.interop.excel 

and

system.data 

which imported file.

you have explicitly reference correct namespace return type of populatevendorgridview:

public system.data.datatable populatevendorgridview() {     ...