Let’s say you have two input DataTables named dt1 and dt2.
And then try below expression to get the required output.
dtOutput = ( From row1 in dt1 Join row2 in dt2 on row1("mat").ToString.Trim.Equals(row2("mat").ToString.Trim) Select dtOutput.Rows.Add({row1("Column1").ToString, row1("Column2").ToString, ...row2("Column1").ToString, row2("Column2").ToString...})).CopyToDataTable
Note: Mention all the required columns from both the tables.