Program Visual C# Filter pada DataGridView

Class Form1
Variabel Komponen	Event	Source Code
Form1	Load	private void Form1_Load(object sender, EventArgs e) {  DataColumn Nama  = new DataColumn("Nama", Type.GetType("System.String"));     DataColumn Waktu = new DataColumn("Waktu", Type.GetType("System.Decimal"));     DataColumn Harga = new DataColumn("Harga", Type.GetType("System.Decimal"));           DataColumn Total_Harga = new DataColumn("Total Harga", Type.GetType("System.Decimal"));           Total_Harga.Expression = "Harga * Waktu";             dt.Columns.Add(Nama);             dt.Columns.Add(Waktu);             dt.Columns.Add(Harga);           dt.Columns.Add(Total_Harga);    }
btnInputData	Click	private void btnInputData_Click(object sender, EventArgs e) { dt.Rows.Add(txtNama.Text, txtWaktu.Text, txtHarga.Text);                          dgv.DataSource = dt; }
btnDeleteSelectedData	Click	private void btnDeleteSelectedData_Click(object sender, EventArgs e) {   {      foreach (DataGridViewCell oneCell in dgv.SelectedCells)      {         if (oneCell.Selected)                     dgv.Rows.RemoveAt(oneCell.RowIndex);       }    } }
btnFilterWaktu	Click	private void btnFilterWaktu_Click(object sender, EventArgs e)         {             DataTable NewDT = new DataTable();             NewDT = dt.Copy();             NewDT.DefaultView.RowFilter = "Waktu = ' " + txtFilterWaktu.Text + " ' ";             dgv.DataSource = NewDT;        }
btnFilterHarga	Click	private void btnFilterHarga_Click(object sender, EventArgs e)         {             DataTable NewDT = new DataTable();              NewDT = dt.Copy();                                                   NewDT.DefaultView.RowFilter = "Harga = ' " + txtFilterHarga.Text + " ' ";                  dgv.DataSource = NewDT;                     }
btnResetFilter	Click	private void btnResetFilter_Click(object sender, EventArgs e)         {             DataTable NewDT = new DataTable();             NewDT = dt.Copy();             dgv.DataSource = NewDT;         }