Kindly try with this expression
dt1.AsEnumerable().Where(function(row) dt2.AsEnumerable().Select(function (r) convert.ToInt32(r(colname.ToString)).Any(function(x) x = Convert.ToInt32(row(colname.ToString))).CopyToDataTable()
solved, just change place of datatable into query,
In_DataTable2.AsEnumerable().Where(Function(row) Not In_DataTable1.AsEnumerable().Select(Function(r) r.Field(Of String)(colname.ToString)).Any(Function(x) x = row.Field(Of String)(colname.ToString))).CopyToDataTable()