Populate a date Label with selected value from a dropdownlist in GridView. This is not working.

[samflex]

Greetings again all and pray that everyone is staying safe. I have a requirement to select a value from a dropdownlist, and upon selecting a value, a label control will be automatically populated with a date value. We are using GridView control. So far, we are running into issues. When I run the code and select a value from the ddlSpeakerName1 dropdownlist control, I get the following error: System.NullReferenceException: 'Object reference not set to an instance of an object.' and the error is on this line:

         txtsDateFilmed1.Text = sdr\["dateAdded"\].ToString();

This is not true. I know I am doing something wrong and would greatly appreciate the assistance as always. Here is some relevant code and select a value //MARKUP

//C#

protected void OnDataBound(object sender, EventArgs e)
{
    DropDownList ddlSpeakerName1 = SermonDetails.FooterRow.FindControl("ddlSpeakerName1") as DropDownList;
    ddlSpeakerName1.DataSource = GetData("SELECT DISTINCT EmployeeID, EmployeeName FROM Employees");
    ddlSpeakerName1.DataTextField = "EmployeeName";
    ddlSpeakerName1.DataValueField = "EmployeeID";
    ddlSpeakerName1.DataBind();
    ddlSpeakerName1.Items.Insert(0, new ListItem("Select Speakers", "0"));
}

protected void ddlSpeakerName1\_SelectedIndexChanged(object sender, EventArgs e)
{
    DropDownList ddlSpeakerName1 = SermonDetails.FooterRow.FindControl("ddlSpeakerName1") as DropDownList;
    TextBox txtsDateFilmed1 = SermonDetails.FooterRow.FindControl("txtsDateFilmed1") as TextBox;

    String strConnString = ConfigurationManager.AppSettings\["XPhiasResultString"\].ToString();
    String strQuery = "select dateAdded from Employees where" +
                      " EmployeeID = @employeeID AND dateAdded IS NOT NULL";
    SqlConnection con = new SqlConnection(strConnString);
    SqlCommand cmd = new SqlCommand();
    cmd.Parameters.AddWithValue("@employeeID", ddlSpeake