Populate (Bind) data from Database in ASP.Net DetailsView control Example

Please refer this code

HTML

<form id="form1" runat="server">
<div>
    <asp:DropDownList ID="ddlEmployees" runat="server" OnSelectedIndexChanged="ddlEmployees_OnSelectedIndexChanged"
        AutoPostBack="true">
    </asp:DropDownList>
    <br />
    <hr />
    <br />
    <table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <td>
                Id
            </td>
            <td>
                <asp:TextBox ID="txtEmployeeId" runat="server" Text='<%# Eval("EmployeeId") %>' />
            </td>
        </tr>
        <tr>
            <td>
                Name
            </td>
            <td>
                <asp:TextBox ID="txtName" runat="server" Text='<%# Eval("FirstName") %>' />
            </td>
        </tr>
        <tr>
            <td>
                Country
            </td>
            <td>
                <asp:TextBox ID="txtCountry" runat="server" Text='<%# Eval("Country") %>' />
            </td>
        </tr>
    </table>
</div>
</form>

Namespaces

using System;
using System.Configuration;
using System.Data.SqlClient;

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        PopulateDropDownList();
    }
}

private void PopulateDropDownList()
{
    string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT EmployeeId, FirstName From Employees ", con))
        {
            con.Open();
            this.ddlEmployees.DataSource = cmd.ExecuteReader();
            this.ddlEmployees.DataTextField = "FirstName";
            this.ddlEmployees.DataValueField = "EmployeeId";
            this.ddlEmployees.DataBind();
            con.Close();
        }
    }
}

protected void ddlEmployees_OnSelectedIndexChanged(object sender, EventArgs e)
{
    int employeeId;
    int.TryParse(this.ddlEmployees.SelectedItem.Value, out employeeId);
    string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT EmployeeId, FirstName, Country From Employees WHERE EmployeeId = @EmployeeId", con))
        {
            cmd.Parameters.AddWithValue("@EmployeeId", employeeId);
            cmd.Connection = con;
            con.Open();
            SqlDataReader sdr = cmd.ExecuteReader();
            if (sdr.Read())
            {
                this.txtEmployeeId.Text = sdr.GetInt32(0).ToString();
                this.txtName.Text = sdr.GetString(1);
                this.txtCountry.Text = sdr.GetString(2);
            }
            con.Close();
        }
    }
}