how to display the value of the column in drop down list

Question

i need to show the selected value from database in drop down list and this drop down list contains items on of them is the selected one from database 

 

asp.net code

 <asp:DropDownList ID="DropDownList3" runat="server" EnableViewState="true" DataSourceID="SqlDataSource7"   AppendDataBoundItems="true" DataTextField="Name" DataValueField="SId" Width="130px" Height="25px"> <asp:ListItem>Select School</asp:ListItem> </asp:DropDownList>
 <asp:SqlDataSource ID="SqlDataSource7" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>" SelectCommand="SELECT [SId],[Name] FROM [School]"></asp:SqlDataSource>






 SqlDataReader myReader = null;
            SqlCommand query = new SqlCommand(@"select * from dbo.Cousres INNER JOIN dbo.School ON
                dbo.School.SId=dbo.Cousres.SId where dbo.Cousres.CourseId='" + TextBox7.Text + "'", conn);
            SqlDataAdapter da = new SqlDataAdapter();
            myReader = query.ExecuteReader();
            while (myReader.Read())
            {
                TextBox3.Text = (myReader["CourseId"].ToString());
                TextBox4.Text = (myReader["CousreName"].ToString());
                DropDownList3.SelectedValue= (myReader["Name"].ToString());
                Edit.Visible = false;
            }

please help  

 thnak you