title: FileUpload.HasFile give always false
body: <p>this is my code where my FileUpload control is outside of update panel but when I click on save button which is under update panel give fileUploadAttachment.HasFile = false</p>
  
  <p>ASPX </p>
  
  <pre><code>&lt;asp:Literal runat="server" ID="lblAttachment" Text="Attachment:" /&gt;&lt;asp:FileUpload
              ID="fileUploadAttachment" runat="server" Width="488px" /&gt;
          &lt;asp:UpdatePanel ID="updatePanelAction" runat="server" UpdateMode="Always"&gt;
              &lt;ContentTemplate&gt;
                  &lt;asp:Button ID="btnSave" runat="server" Text="Save" OnClick="btnSave_Click" ValidationGroup="Save" /&gt;
                  &lt;asp:Button ID="btnTest" runat="server" Text="Test" Enabled="false" OnClick="btnTest_Click" /&gt;
                  &lt;asp:Button ID="btnConfirmTest" runat="server" Text="Confirm Test" Enabled="false"
                      OnClick="btnConfirmTest_Click" /&gt;
                  &lt;asp:Button ID="btnSend" runat="server" Text="Send" Enabled="false" OnClick="btnSend_Click" /&gt;
              &lt;/ContentTemplate&gt;
  
          &lt;/asp:UpdatePanel&gt;
  </code></pre>
  
  <p>CS</p>
  
  <pre><code>protected void btnSave_Click(object sender, EventArgs e)
  {
      CampaignBAL campaignBAL;
      string tmpFileName = "";
      User user;
      Campaign campaignDetail = new Campaign();
      int? campaignID;
  
      if (fileUploadAttachment.HasFile) // return always false
      {
          tmpFileName = string.Format("{0}\\{1}{2}", Server.MapPath("TempUpload"), Guid.NewGuid(), Path.GetExtension(fileUploadAttachment.PostedFile.FileName));
          fileUploadAttachment.PostedFile.SaveAs(tmpFileName);
      }
  }
  </code></pre>
  
  <p>please help me how can I fix it</p>