Error: SqlDataAdapter does not contain a definition for Fill and no extension method Fill accepting a first argument of type SqlDataAdapter could be found in ASP.Net

Hi,

I am using SqlDataAdapter in asp.net c# but a strange error i am facing can sombody assist me to fix it! SqlDataAdapter' does not contain a definition for 'Fill' and no extension method 'Fill' accepting a first argument of type 'SqlDataAdapter' could be found (are you missing a using directive or an assembly reference? SqlDataAdapter' does not contain a constructor that takes 1 arguments

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Regards

firoz khan