The ConnectionString property has not been initialized.

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string

connection

Hi
why this error happened?
Here is tow DropDownList control when I Select a field from first dropdownllist I face to the below error.

The ConnectionString property has not been initialized.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Quote:

Exception Details: System.InvalidOperationException: The ConnectionString property has not been initialized.
Line 203: sqlCmd.Parameters.AddWithValue("@FieldID", DropDownList_PersonField.SelectedValue);
Line 204: sqlCmd.Connection = con;
Line 205: con.Open();
Line 206: SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
Line 207: DataTable dt = new DataTable();
Source File: e:\Final Project\FindEeasyJobs\ManagePersons.aspx.cs Line: 205

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my C# cod

protected void DropDownList_PersonField_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            using (SqlCommand sqlCmd = new SqlCommand())
            {
                sqlCmd.CommandText = "select SubField_ID,SubField_Name_english FROM SubField_TB WHERE Field_ID=@FieldID";
                sqlCmd.Parameters.AddWithValue("@FieldID", DropDownList_PersonField.SelectedValue);
                sqlCmd.Connection = con;
                con.Open();
                SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
                DataTable dt = new DataTable();
                da.Fill(dt);
                DropDownList_PersonSubField.DataSource = dt;
                DropDownList_PersonSubField.DataValueField = "SubField_ID";
                DropDownList_PersonSubField.DataTextField = "SubField_Name_english";
                DropDownList_PersonSubField.DataBind();
                con.Close();
                //Adding "Please select SubField" option in dropdownlist
                DropDownList_PersonSubField.Items.Insert(0, new ListItem("Please select your field", "0"));
            }
        }
        catch (System.Data.SqlClient.SqlException ex)
        {
            string msg = "Fetch Error:";
            msg += ex.Message;
            throw new Exception(msg);
        }
    }//-------------------end of selectindexchanged