Why is one section of code working, but the other not?

Question

Here is the code that works:

protected void submitForMail(object sender, EventArgs e)
{
    string constr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\TravelJoansDB.mdb;";
    string cmdstr = "INSERT INTO EmailList(FirstName,LastName,EmailAddress) VALUES (@FirstName, @LastName, @EmailAddress)";

    OleDbConnection con = new OleDbConnection(constr);
    OleDbCommand com = new OleDbCommand(cmdstr, con);

    TextBox tFirstName = (TextBox)FormView1.FindControl("FirstName");
    TextBox tLastName = (TextBox)FormView1.FindControl("LastName");
    TextBox tEmail = (TextBox)FormView1.FindControl("EmailAddress");

    con.Open();
    com.Parameters.AddWithValue("@FirstName", tFirstName.Text);
    com.Parameters.AddWithValue("@LastName", tLastName.Text);
    com.Parameters.AddWithValue("@EmailAddress", tEmail.Text);
    com.ExecuteNonQuery();
    con.Close();
}

Here is the code that doesn't:

protected void UpdatePic(object sender, EventArgs e)
{
    string constr = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\TravelJoansDB.mdb;";
    string cmdstr = "INSERT INTO BlogEntryItems(Picture) VALUES (@UpdatedPic)";

    OleDbConnection con = new OleDbConnection(constr);
    OleDbCommand com = new OleDbCommand(cmdstr, con);

    TextBox uPic = (TextBox)DataList1.FindControl("BEIPictureField");

    con.Open();
    com.Parameters.AddWithValue("@UpdatedPic", uPic.Text);
    com.ExecuteNonQuery();
    con.Close();
}

Here is the code containing the Datalist1 control:

<asp:AccessDataSource ID="AccessDataSource1" runat="server" 
    DataFile="~/App_Data/TravelJoansDB.mdb" 
    SelectCommand="SELECT * FROM Table2 INNER JOIN [BlogEntryItems] ON Table2.ID=BlogEntryItems.BlogID WHERE ID=@ID" >
    <SelectParameters>
        <asp:QueryStringParameter Name="ID" QueryStringField="ID" />
    </SelectParameters>
</asp:AccessDataSource>
<asp:DataList ID="DataList1" runat="server" DataSourceID="AccessDataSource1">
<ItemStyle />
<ItemTemplate>
    <table>
        <tr>
            <td>
                <br />
                <asp:Image ID="Image1" CssClass="placePicCenter" runat="server" 
                BorderWidth="1px"
                BorderColor="#EEEEEE"
                ImageUrl='<%# "PlaceImages/" + Eval("Picture") %>' /><br />
                <asp:TextBox ID="BEIPictureField" runat="server" Text='<%# Bind("Picture") %>' /><br />
                <asp:Button ID="UpdatePicButton" runat="server" Text="Update" OnClick="UpdatePic" />
                <br />
            </td>
        </tr>
        <tr>
            <td>
                <asp:Label ID="Label4" CssClass="placeBodyStyle" runat="server" Text='<%# Eval("PicText1") %>' />
            </td>
        </tr>
        <tr>
            <td>
                &nbsp;
            </td>
        </tr>
    </table>
</ItemTemplate>
</asp:DataList>

These blocks of code are for two different buttons on two different pages. The error I get when I run the second block of code is "Object reference not set to an instance of an object." Any help would be appreciated.

Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Oct 02 '13 at 02:37
I understand that it is saying it is not initialized, but why is the first section of code working that is for another button on another page in my site. — Joseph, Oct 02 '13 at 02:49

Ahsan · Accepted Answer · 2013-10-02T02:44:11.687

4

This line is the probable cause, it is failing to find the control BEIPictureField thus the "Object reference not set to an instance of an object." error

TextBox uPic = (TextBox)DataList1.FindControl("BEIPictureField");

EDIT 1

Try this:

TextBox uPic = (TextBox)DataList1.Items[1].FindControl("BEIPictureField");

you will have to rewrite your logic to find the control in each item not the DataList since it is the parent you will not find it there.

edited Oct 02 '13 at 02:44

answered Oct 02 '13 at 02:30

Ahsan

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2

Also possible that `DataList1` is `null`. – Jay Oct 02 '13 at 02:32
Check my edited question. Why wouldn't it be able to find the control? – Joseph Oct 02 '13 at 02:37
@Joseph Please debug your code. i just gave a suggestion with the above example. this would only fetch item 1 in your datalist, if you have many items in the list you need to process them individually. – Ahsan Oct 02 '13 at 03:03

Why is one section of code working, but the other not?

1 Answers1