Rebind selected value to DropDownList from Database using C# in ASP.Net

Hi yohana,

I have created sample code which fullfill your requirement.

HTML

Default.aspx Page

<form id="form1" runat="server">
<div>
    <table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <td>
                Name:
            </td>
            <td>
                <asp:TextBox ID="txtName" runat="server" />
            </td>
        </tr>
        <tr>
            <td>
                <br />
            </td>
        </tr>
        <tr>
            <td>
                State:
            </td>
            <td>
                <asp:DropDownList ID="ddlState" runat="server">
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td>
                <br />
            </td>
        </tr>
        <tr>
            <td>
                Country:
            </td>
            <td>
                <asp:DropDownList ID="ddlCountry" runat="server">
                </asp:DropDownList>
            </td>
        </tr>
    </table>
    <br />
    <asp:Button ID="btnAdd" Text="Add" OnClick="OnAdd" runat="server" />
</div>
</form>

C#

private string constr = ConfigurationManager.ConnectionStrings["Constring"].ToString();
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {

        this.GetCountry();
        this.GetState();
        if (Request.QueryString["Id"] != null)
        {
            GetEdit();
        }
    }
}

private void GetEdit()
{

    using (SqlConnection con = new SqlConnection(constr))
    {
        SqlCommand cmd = new SqlCommand("SELECT  * FROM UserDetails WHERE Id='" + Request.QueryString["Id"] + "'", con);
        con.Open();
        SqlDataReader idr = cmd.ExecuteReader();
        if (idr.Read())
        {
            txtName.Text = idr["Name"].ToString();
            ddlState.Text = idr["State"].ToString();
            ddlCountry.Text = idr["Country"].ToString();
        }
        con.Close();

    }
}

private void GetState()
{
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT  * FROM State", con))
        {
            DataTable dt = new DataTable();
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            sda.Fill(dt);
            ddlState.DataSource = dt;
            ddlState.DataTextField = "StateName";
            ddlState.DataValueField = "StateId";
            ddlState.DataBind();
            ddlState.Items.Insert(0, new ListItem("---SELECT State---"));
        }
    }
}

private void GetCountry()
{
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT  * FROM Country", con))
        {
            DataTable dt = new DataTable();
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            sda.Fill(dt);
            ddlCountry.DataSource = dt;
            ddlCountry.DataTextField = "CountryName";
            ddlCountry.DataValueField = "CountryId";
            ddlCountry.DataBind();
            ddlCountry.Items.Insert(0, new ListItem("---SELECT Country---"));
        }
    }
}

protected void OnAdd(object sender, EventArgs e)
{
    using (SqlConnection con = new SqlConnection(constr))
    {
        SqlCommand cmd = new SqlCommand("INSERT INTO UserDetails VALUES(@Name,@State,@Country)", con);
        cmd.CommandType = CommandType.Text;
        cmd.Parameters.AddWithValue("@Name", txtName.Text.Trim());
        cmd.Parameters.AddWithValue("@State", ddlState.SelectedItem.Value);
        cmd.Parameters.AddWithValue("@Country", ddlCountry.SelectedItem.Value);
        con.Open();
        cmd.ExecuteNonQuery();
        con.Close();
    }

    Response.Redirect("Profileview.aspx");
}

HTML

Profileview.aspx Page

<form id="form1" runat="server">
<div>
    <asp:HiddenField ID="hidId" runat="server" />
    <br />
    Name:<asp:Label ID="lblName" Text="" runat="server" />
    <br />
    State:
    <asp:Label ID="ddlState" Text="" runat="server" />
    <br />
    Country:<asp:Label ID="ddlCountry" Text="" runat="server" />
</div>
<asp:LinkButton ID="btnEdit" Text="Edit" OnClick="OnEdit" runat="server" />
</form>

C#

private string constr = ConfigurationManager.ConnectionStrings["Constring"].ToString();
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.GetProfile();
    }
}

private void GetProfile()
{
    using (SqlConnection con = new SqlConnection(constr))
    {
        SqlCommand cmd = new SqlCommand("SELECT  Id,Name,StateName,CountryName FROM UserDetails INNER JOIN State ON UserDetails.State=StateId INNER JOIN Country ON Country .CountryID = UserDetails.Country", con);
        con.Open();
        SqlDataReader idr = cmd.ExecuteReader();
        if (idr.Read())
        {
            hidId.Value = idr["Id"].ToString();
            lblName.Text = idr["Name"].ToString();
            ddlState.Text = idr["StateName"].ToString();
            ddlCountry.Text = idr["CountryName"].ToString();
        }
        con.Close();
       btnAdd.Text = "Update";
    }
}

protected void OnEdit(object sender, EventArgs e)
{
    Response.Redirect("Default.aspx?Id=" + hidId.Value);
}

Screenshot