Question

Suppose I have the following asp.net page:

public partial class SamplePage : System.Web.UI.Page
{
    private int UserID;

    protected void Page_Load(object sender, EventArgs e)
    {
    }

    protected void btnSearchUser_Click(object sender, EventArgs e)
    {
       UserID = 5;
    }

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        Response.Write(UserID.ToString());
    }
}

but UserID is always 0. How to achieve it to be 5 always?

Answer 1

Because a Button’s click causes a postback and data is always lost during postbacks as HTTP protocol is stateless.. So you’ll have to store that UserID into a viewstate to maintain its value…and that’s why we have State Mangement’s concept in Asp.net.
However you can achieve it like this…

public partial class SamplePage : System.Web.UI.Page
{
    int UserID;
  protected void Page_Load(object sender, EventArgs e)
  {

  }
 protected void btnSearchUser_Click(object sender, EventArgs e)
 {
    UserID=5;
    ViewState["UserID"] = UserID;
 }
 protected void btnSubmit_Click(object sender, EventArgs e)
 {
    if(ViewState["UserID"]!=null)
    Response.Write(ViewState["UserID"].ToString());
 }
}