ADO.NET :: How To Display Auto - Incrementing Value From Database In The Same Page Where Inserting Value

in my aspx page user is creating a request and when the request is created a request_id is generated automatically in databse..i want to retreive tht particular request_id and display it on the same web page.

here is my code-

protected void Button1_Click(object sender, EventArgs e)
{
String selection = DropDownList1.Text.ToString();
String status = "inactive";
try
{
ConnectionStringSettings set = ConfigurationManager.ConnectionStrings["WATERMARKING"];
String cns = set.ConnectionString;
SqlConnection cnn = new SqlConnection(cns);
cnn.Open();
String query = "Insert into REQUESTS (USERNAME,REQUEST_TYPE,STATUS) values ('" + uName + "','" + selection + "','" + status + "')";
SqlCommand cmd = new SqlCommand(query, cnn);
cmd.ExecuteNonQuery();
//Response.Write("Request created Successfully ");
//MessageBox.Show("request created successfully");
Label4.Visible.Equals(true);
Label4.Text="request created successfully";
Label5.Text = "Your Request ID is";
Label6.Text = "ID required to Check the Request Status";
}
catch (Exception err)
{
//Response.Write("error generated while raising request"+err);
Label4.Visible.Equals(true);
Label4.Text = "request creation error"+err;
}
}

here wen a value is getting inserted in REQUESTS table a column named REQUEST_ID gets populated and i want to display that value on the web page