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Object reference not set to an instance of an object.

Posted on 2013-05-22
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Last Modified: 2013-06-03
In button click event, I got this error. I am not sure why.
Object reference not set to an instance of an object.


  Dim filename As String
   
  filename = Me.FileUpload1.PostedFile.FileName
code.txt
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Question by:VBdotnet2005
2 Comments
 
LVL 23

Expert Comment

by:Ioannis Paraskevopoulos
ID: 39191321
Hi,

Try the following code:
        filename = CType(Page.FindControl("FileUpload1"), FileUpload).PostedFile.FileName

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Giannis
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LVL 12

Accepted Solution

by:
Jitendra Patil earned 500 total points
ID: 39193921
Hi

The problem lies in your aspx code.

You need to add a trigger to your update panel as given below
</ContentTemplate>
            <Triggers>
              <asp:PostBackTrigger ControlID="btnUpload" />
            </Triggers>
        </asp:UpdatePanel>


view the complete code here
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
   
    <div>
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel_1" runat="server">
            <ContentTemplate>
                <table>
                    <tr>
                        <td>
                            Upload File
                            <asp:FileUpload ID="FileUpload1" runat="server" Size="100" />&nbsp;&nbsp;
                            <asp:Button ID="btnUpload" runat="server" Text="Upload" />
                            &nbsp;<br />
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" CellPadding="4"
                                DataKeyNames="ID" DataSourceID="SqlDataSource1" ForeColor="#333333" GridLines="Vertical"
                                HorizontalAlign="Center" Width="100%">
                                <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                                <Columns>
                                    <asp:TemplateField>
                                        <ItemTemplate>
                                            <asp:CheckBox ID="CheckBox1" runat="server" />
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:BoundField DataField="CustomerID" HeaderText="CustomerID" SortExpression="CustomerID" />
                                    <asp:TemplateField HeaderText="filename">
                                        <ItemTemplate>
                                            <asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl='<%# string.format("test.aspx?={0}", Databinder.Eval(container.Dataitem, "filename")) %>'
                                                Text='<%# Databinder.Eval(container.dataitem, "filename") %>'></asp:HyperLink>
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:BoundField DataField="ID" HeaderText="ID" SortExpression="ID" Visible="false" />
                                    <asp:BoundField DataField="map_client" HeaderStyle-HorizontalAlign="Center" HeaderText="Map Columns"
                                        ItemStyle-HorizontalAlign="Center" Visible="true" />
                                </Columns>
                                <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
                                <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
                                <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" HorizontalAlign="Left" />
                                <EditRowStyle BackColor="#999999" />
                                <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
                                <EmptyDataTemplate>
                                    <table bgcolor="#5D7B9D" style="width: 100%; border-style: solid; border-width: 1px">
                                        <tr>
                                            <td style="color: #FFFFFF">
                                                <center>
                                                    No Data Found</center>
                                            </td>
                                        </tr>
                                    </table>
                                </EmptyDataTemplate>
                            </asp:GridView>
                            <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:myconConnectionString %>"
                                ProviderName="System.Data.SqlClient" SelectCommand="mysp"
                                SelectCommandType="StoredProcedure"></asp:SqlDataSource>
                            <asp:Button ID="Button1" runat="server" Text="Button" Visible="False" />
                            <asp:LinkButton ID="LinkButton1" runat="server">Clear</asp:LinkButton>
                            <br />
                        </td>
                    </tr>
                </table>
            </ContentTemplate>
             <Triggers>
              <asp:PostBackTrigger ControlID="btnUpload" />
            </Triggers>
        </asp:UpdatePanel>
        <asp:UpdateProgress ID="UpdateProgress2" runat="server" AssociatedUpdatePanelID="UpdatePanel_1">
            <ProgressTemplate>
                <div id="progress" align="center" valign="middle" runat="server" style="border-width: thin;
                    border-color: black; position: absolute; left: 0%; top: 4%; visibility: visible;
                    vertical-align: middle; background-color: White; z-index: 40;">
                    <table width="1054px" height="510px">
                        <tr>
                            <td>
                                Please wait...<br />
                                <br />
                                <img src="image/test.gif" />
                            </td>
                        </tr>
                    </table>
                </div>
            </ProgressTemplate>
        </asp:UpdateProgress>
    </div>
</asp:Content>

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your backend code is working fine.

once you add a trigger to your  update panel you will get the desired result without performing a full postback, it will be a partial post back and you update panel will know that this button needs an action to be done.

hope this helps.
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