e.Item.FindControl抛出未设置为对象实例的对象引用

Question

Here is the part of Repeater code that throws exception... "Computer.Administrators" is StringCollection object. Debugger shows that "AdminsEnumerator.Current" gets correct string value but when "txtAdministrators.Text" tries to set value - exception is thrown. Please help with ideas.

<asp:Repeater ID="repeatAdministrators" OnItemDataBound="repeatAdministrators_ItemDataBound" runat="server">
    <HeaderTemplate>
        <tr>
            <td class="formLabel">
                Administrators:
            </td>
            <td class="formInputText">
    </HeaderTemplate>
    <ItemTemplate>
        <asp:TextBox ID="txtAdministrators" runat="server" MaxLength="50" Enabled="False"></asp:TextBox><br />
    </ItemTemplate>
    <FooterTemplate>
        </td> </tr>
        <tr>
    </FooterTemplate>
</asp:Repeater>

And here is code behind.

 protected void btnPing_Click(object sender, EventArgs e)
    {
        //...

        repeatAdministrators.DataSource = Computer.Administrators;
        repeatAdministrators.DataBind();
    }

    protected void repeatAdministrators_ItemDataBound(object sender, RepeaterItemEventArgs e)
    {
        TextBox txtAdministrators = e.Item.FindControl("txtAdministrators") as TextBox;
        StringEnumerator AdminsEnumerator = Computer.Administrators.GetEnumerator();

        while (AdminsEnumerator.MoveNext())
        {
            txtAdministrators.Text = AdminsEnumerator.Current;
        }
    }

Answer 1

You need to make sure you're not in a header item:

if(e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
}

(sorry, this is from memory, but that should go in your ItemDataBound method)