(Web app)ถ้าจะเช็คว่าเลข id ที่จะนำเข้า database ไม่ตรงกับ id ที่มีอยู่ใน database นี่เช็คยังไงหรอครับ

    void btnSave_Click(Object sender , EventArgs e)        
	{ 
			int intNumRows;
			strSQL = "SELECT COUNT(*) FROM customer WHERE CustomerID = '"+ this.txtCustomerID.Text +"' ";
			objCmd = new SqlCommand(strSQL, objConn);
			intNumRows = Convert.ToInt32(objCmd.ExecuteScalar());

			if(intNumRows > 0)
			{
				this.pnlAdd.Visible = false;
				this.lblStatus.Visible = true;
				this.lblStatus.Text = "CustomerID already exists.";
			}
			else
			{
				strSQL = "INSERT INTO customer (CustomerID,Name,Email,CountryCode,Budget,Used) " +
				" VALUES " +
				" ('" + this.txtCustomerID.Text + "','" + this.txtName.Text + "','" + this.txtEmail.Text + "', " +
				" '" + this.txtCountryCode.Text + "','" + this.txtBudget.Text + "','" + this.txtUsed.Text + "')";

				objCmd = new SqlCommand();
				objCmd.Connection = objConn;
				objCmd.CommandText = strSQL;
				objCmd.CommandType = CommandType.Text;
								
				this.pnlAdd.Visible = false;

				try
				{
					objCmd.ExecuteNonQuery();
					this.lblStatus.Text = "Record Inserted";
					this.lblStatus.Visible = true;
				}
				catch (Exception ex)
				{
					this.lblStatus.Visible = true;
					this.lblStatus.Text = "Record can not insert Error ("+ ex.Message +")";
				}
		}
    }

    Sub btnSave_Click(sender As Object, e As EventArgs)   	
			Dim intNumRows As Integer
			strSQL = "SELECT COUNT(*) FROM customer WHERE CustomerID = '"& Me.txtCustomerID.Text &"' "		
			objCmd = New SqlCommand(strSQL, objConn)
			intNumRows = objCmd.ExecuteScalar()

			IF intNumRows > 0 Then
				Me.pnlAdd.Visible = False
				Me.lblStatus.Visible = True
				Me.lblStatus.Text = "CustomerID already exist."
			Else	
			

				strSQL = "INSERT INTO customer (CustomerID,Name,Email,CountryCode,Budget,Used) " & _
				" VALUES " & _
				" ('" & Me.txtCustomerID.Text & "','" & Me.txtName.Text & "','" & Me.txtEmail.Text & "', " & _
				" '" & Me.txtCountryCode.Text & "','" & Me.txtBudget.Text & "','" & Me.txtUsed.Text & "')"

				objCmd = New SqlCommand
				With objCmd
				   .Connection = objConn
				   .CommandText = strSQL
				   .CommandType = CommandType.Text		   
				End With
								
				Me.pnlAdd.Visible = False
				Try
					objCmd.ExecuteNonQuery()            
					Me.lblStatus.Text = "Record Inserted"
					Me.lblStatus.Visible = True
				Catch ex As Exception
					Me.lblStatus.Visible = True
					Me.lblStatus.Text = "Record can not insert Error ("& ex.Message &")"
				End Try

		End IF