aspx update button not updating all fields

Question

I have an update button and when clicked, it updates all the fields in my sql table except for the "Channel" field.

protected void btnupdate_Click(object sender, EventArgs e)
        {
            if (TextBox1.Text != "" && TextBox2.Text != "" && TextBox3.Text != "" && DropDownList1.SelectedValue != "")
            {
                using (con = new SqlConnection(cs))
                {
                    con.Open();
                    cmd = new SqlCommand("Update Assigned_Radio_Channels Set Channel=@Channel, Agency_Assigned_To_Channel=@Agency_Assigned_To_Channel, Dates=@Dates, Assigned_By=@Assigned_By, Notes=@Notes where Channel=@Channel", con);
                    cmd.Parameters.AddWithValue("@Channel", DropDownList1.SelectedValue);
                    cmd.Parameters.AddWithValue("@Agency_Assigned_To_Channel", TextBox1.Text);
                    cmd.Parameters.AddWithValue("@Dates", TextBox2.Text);
                    cmd.Parameters.AddWithValue("@Assigned_By", TextBox3.Text);
                    cmd.Parameters.AddWithValue("@Notes", TextBox4.Text);
                    cmd.ExecuteNonQuery();
                    con.Close();
                    DataLoad();
                    ClearAllData();
                }
            }
            else
            {
                lblMessage.Text = "Fill In All Information";
            }

Answer 1

Try getting the value of the selected item.

DropDownList1.SelectedItem.Value

Reference Docs

https://learn.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.dropdownlist?view=netframework-4.8.1

Answer 2

I needed to add the ID field to make it work

protected void btnupdate_Click(object sender, EventArgs e)
        {
            if (TextBox1.Text != "" && TextBox2.Text != "" && TextBox3.Text != "" && DropDownList1.SelectedValue != "")
            {
                using (con = new SqlConnection(cs))
                {
                    con.Open();
                    cmd = new SqlCommand("Update Assigned_Radio_Channels Set Channel=@Channel, Agency_Assigned_To_Channel=@Agency_Assigned_To_Channel, Dates=@Dates, Assigned_By=@Assigned_By, Notes=@Notes where ID=@ID", con);
                    cmd.Parameters.AddWithValue("@Channel", DropDownList1.SelectedItem.Text);
                    cmd.Parameters.AddWithValue("@Agency_Assigned_To_Channel", TextBox1.Text);
                    cmd.Parameters.AddWithValue("@Dates", TextBox2.Text);
                    cmd.Parameters.AddWithValue("@Assigned_By", TextBox3.Text);
                    cmd.Parameters.AddWithValue("@Notes", TextBox4.Text);
                    cmd.Parameters.AddWithValue("@ID", TextBox5.Text);
                    cmd.ExecuteNonQuery();
                    con.Close();
                    DataLoad();
                    ClearAllData();
                }
            }
            else
            {
                lblMessage.Text = "Fill In All Information";
            }
        }