File Upload file vanishes after postback

Usually this thing happens if you are using script manager and update panel in your page. While clicking the submit button or when a postback happens, your file upload's file vanishes and FileUpload1.HasFile always returns false. There are several ways to handle this.


Process-1 : Add a trigger to your Update Panel.

<Triggers>

               

<asp:PostBackTrigger ControlID="Button1" />

</Triggers>

Process-2 : If your page is having a Master Page and your update panel is present there in the master page,then you have to dynamically add a trigger to the master page's update panel from the child page.

public void AddTrigger()

{

     PostBackTrigger trigger=new PostBackTrigger();

     trigger.ControlID=btn.UniqueID;

     UpdatePanel updt = (UpdatePanel)this.Master.FindControl("UpdatePanel1");

     updt.Triggers.Add(trigger);

 }

Then, call this method in the Page_Load Event.

    

    protected void Page_Load(object sender, EventArgs e)

    {

        AddTrigger();

    }

Process-3: 

protected void Page_Load(object sender, EventArgs e)

{

    ScriptManager.GetCurrent(this).RegisterPostBackControl(btn);

}

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