how to check for NULL in DataTable

how to check datatable is empty

In think, you are using  dtUserSettingvalues before initialization and dtUserSettingvalues does not have any reference to DataTabe object so that is why you are getting this error, if there is such case in your code then you can do this check in this way

if ((dtUserSettingvalues != null) && (dtUserSettingvalues.Rows.Count != 0))

    {

    //do your code

    }