Try
dt.DefaultView.RowFilter = "LabelRef like '%" + TextBox2.Text + "%'"
Note if you are using a date column to filter then the syntax may depend on the driver (data provider) and you need to drop the wildcard character, so it would be
dt.DefaultView.RowFilter = "LabelRef = '" + TextBoxDate.Text + "'"
or
dt.DefaultView.RowFilter = "LabelRef = #" + TextBoxDate.Text + "#"