Dim dt As New DataTable
With dt
  .Columns.Add("Material")
  .Rows.Add("Eisen")
  .Rows.Add("Stahl")
  .Rows.Add("Eisen")
  .Rows.Add("Eisen")
  .Rows.Add("Alu")
  .Rows.Add("Eisen")
  .Rows.Add("Stahl")
  .Rows.Add("Eisen")
End With
 
DataGridView2.DataSource = (From d As DataRow In dt.AsEnumerable() _
Group d By Material = d.Field(Of String)("Material") Into _
g = Group Select Material, g.Count).tolist()