Null Reference Objection. Object reference not set to an instance of an object

Question

1.00/5 (3 votes)

See more:

Hi All,

I am getting the above error while i have linked a datatable to a dropdownlist in asp.net Grid view in Footer for Insert.

I have checked in immediate window and datatable is having 2 records (datatable.rows.count).

following is the code in asp and vb... Please sugggest

Asp.

XML

<asp:TemplateField HeaderText="Type" HeaderStyle-HorizontalAlign="Center">
                <EditItemTemplate>
                    <asp:DropDownList ID="ddlGridType" runat="server" DataTextField="BOMIT" DataValueField="BOMIT"> </asp:DropDownList>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="lblGridType" runat="server" Text='<%# Eval("BOMIT")%>'></asp:Label>
                </ItemTemplate>
                <FooterTemplate>
                    <asp:DropDownList ID="ddlNewGridType" runat="server" DataTextField="BOMIT" DataValueField="BOMIT"> </asp:DropDownList>
                 </FooterTemplate>
            </asp:TemplateField>

VB:

VB

Protected Sub DataGridView1_RowDataBound(sender As Object, e As GridViewRowEventArgs) Handles DataGridView1.RowDataBound

        If e.Row.RowType = DataControlRowType.Footer Then

            Dim daGridTypes As SqlDataAdapter = New SqlDataAdapter
            daGridTypes.SelectCommand = New SqlCommand("select distinct BOMIT from bom", connection)

            Dim tbGridTypes As DataTable = New DataTable
            connection.Open()
            daGridTypes.Fill(tbGridTypes)
            connection.Close()

            'To SORT THE DATATABLE
            Dim dataGridView As New DataView(tbGridTypes)
            dataGridView.Sort = "BOMIT ASC"
            tbGridTypes = New DataTable
            tbGridTypes = dataGridView.ToTable()

            ddlNewGridType = e.Row.FindControl("ddlNewGridype")

            **********ddlNewGridType.DataSource = tbGridTypes
            ddlNewGridType.DataTextField = "BOMIT"
            ddlNewGridType.DataValueField = "BOMIT"
            ddlNewGridType.DataBind()

        End If

    End Sub

Posted 24-May-14 15:35pm

atul sharma 5126

Add a Solution

Comments

[no name] 24-May-14 21:53pm

You are getting that error for the exact same reason that everyone else gets that error. You are trying to use the methods or properties of an object that has not been instantiated. You need to debug your code and find the object that is null.

atul sharma 5126 24-May-14 22:08pm

Thanks for replying Wes.
I have already tried debugging and mentioned the results within the question.

The error generates on the linking of datasource to dropdownlist (marked with ***)
And i have checked that at the time of linking, datatable has 2 records i.e. it is not Null.

atul sharma 5126 24-May-14 22:11pm

Can the error be related to the other fields which i have not called and also not used directly but may me checked as the event is RowBound event?

2 solutions

Solution 1

you can't directly access control by id inside the templates like item, header or footer
what you can do is Find the control and set the data source. add below line

VB

If e.Row.RowType = DataControlRowType.Footer Then
    Dim ddlNewGridType As DropDownList = DirectCast(e.Row.FindControl("ddlNewGridType"), DropDownList)

Posted 24-May-14 17:35pm

DamithSL

Updated 24-May-14 20:02pm

v2

Comments

atul sharma 5126 25-May-14 1:52am

Thanks for the reply!
Following error showing: 'DropDownList' is as type and cannot be as an expression

DamithSL 25-May-14 2:02am

check my update

atul sharma 5126 25-May-14 2:31am

New error removed. But now stuck on the original error

DamithSL 25-May-14 2:40am

you know how to debug? check what is null? check ddlNewGridType is null or not and tbGridTypes has records

atul sharma 5126 25-May-14 2:45am

ddlNewGridType is a new dropdown list
whereas tbGridTypes has 2 records

DamithSL 25-May-14 3:02am

past the code what you tried here

atul sharma 5126 26-May-14 3:33am

Thanks a lot for your support Damith. It was a typo in control ID of missing 't'

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Matthew Dennis · Accepted Answer · 2014-05-25T00:54:00

You have a typo, missing a letter in the control ID.

C#

ddlNewGridType = e.Row.FindControl("ddlNewGridype")

should be

C#

ddlNewGridType = e.Row.FindControl("ddlNewGridType")

It is always a good idea to check that the returned value is not null, so that you catch and log these errors. This prevents changes to the .aspx file from silently breaking the .aspx.cs file.

C#

ddlNewGridType = e.Row.FindControl("ddlNewGridype")
if (ddlNewGridType == null)
    logger.Error("Oops, I can't find 'ddlNewGridType'.);