Object reference not set to an instance of an object. plz hlp meeeeeeee

Question

1.00/5 (4 votes)

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XML

<div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
            >
            <Columns>
                <asp:TemplateField>
                <HeaderTemplate>
                    <asp:CheckBox ID="main" runat="server" />
                </HeaderTemplate>
                    <EditItemTemplate>
                        <asp:CheckBox ID="CheckBox1" runat="server"/>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:CheckBox ID="CheckBox1" runat="server" />
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Quastion" SortExpression="testq">
                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("testq") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label1" runat="server" Text='<%# Bind("testq") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Anskey" SortExpression="anskey">
                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("anskey") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label2" runat="server" Text='<%# Bind("anskey") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Difflevel" SortExpression="difflevel">
                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("difflevel") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label3" runat="server" Text='<%# Bind("difflevel") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
        <br />
        <asp:Button ID="Button1" runat="server" Text="DELETE" onclick="Button1_Click" />
    </div>

.Cs page:

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
public partial class chchbox : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection(@"Data Source=MAY-PC\SQLEXPRESS;Initial Catalog=demo;Integrated Security=True");
    protected void Page_Load(object sender, EventArgs e)
    {
        bind();
    }
    private void bind()
    {
        con.Open();
        DataTable dt = new DataTable();
        SqlDataAdapter da=new SqlDataAdapter("select * from quastion order by testqid asc",con);
        da.Fill(dt);
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        foreach (GridViewRow row in GridView1.Rows)
        {
            CheckBox Check = (CheckBox)GridView1.FindControl("CheckBox1");
            if (Check.Checked)
            {
                var userid = Convert.ToInt32(GridView1.DataKeys[row.RowIndex].Value);
                SqlCommand cmd = new SqlCommand("delete from quastion where id=@id",con);
                cmd.Parameters.AddWithValue("@id", userid);
                cmd.ExecuteNonQuery();
                con.Close();
                bind();
            }
        }
    }
    private void chacked()
    {
        for (int i = 0; i < GridView1.Rows.Count; i++)
        {
            CheckBox ckd = (CheckBox)GridView1.Rows[i].FindControl("main");
            ckd.Checked = true;
        }
    }
}

Posted 27-Mar-14 0:48am

bhagyadeep

Updated 27-Mar-14 0:53am

Tom Marvolo Riddle

v4

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Comments

Bojjaiah 27-Mar-14 6:52am

debug your solution you are getting null values.

bhagyadeep 27-Mar-14 7:24am

i try to debug but Check.Checkedegt null!!!!!!!!

Krunal Rohit 27-Mar-14 7:16am

At which line ?
Your code almost looks promising to me.

-KR

4 solutions

Solution 5

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx[^],
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx[^].

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx[^].

Good luck,

—SA

Posted 27-Mar-14 8:25am

Sergey Alexandrovich Kryukov

Solution 2

One of those <%#Bind() %> is getting a null value passed

Posted 27-Mar-14 0:50am

Akshay_Randive

Solution 4

you just try to write

HTML

<%# (Convert.ToString(Eval("your field")))%>

in replacement of

HTML

<<%# Bind("your field") %>

Posted 27-Mar-14 2:23am

Ankur Ramanuj

Updated 27-Mar-14 2:24am

v3

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Christian Amado · Accepted Answer · 2014-03-27T15:03:00

You question is fuzzy but let's try this:

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
public partial class chchbox : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection(@"Data Source=MAY-PC\SQLEXPRESS;Initial Catalog=demo;Integrated Security=True");
    protected void Page_Load(object sender, EventArgs e)
    {
        bind();
    }
    private void bind()
    {
        con.Open();
        DataTable dt = new DataTable();
        SqlDataAdapter da=new SqlDataAdapter("select * from quastion order by testqid asc",con);
        da.Fill(dt);
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        foreach (GridViewRow row in GridView1.Rows)
        {
            CheckBox Check = (CheckBox)GridView1.FindControl("CheckBox1");
            //VERIFY IF YOUR CHECKBOX IS NOT NULL
            if (Check != null)
            {
                if (Check.Checked)
                {
                    var userid = Convert.ToInt32(GridView1.DataKeys[row.RowIndex].Value);
                    SqlCommand cmd = new SqlCommand("delete from quastion where id=@id",con);
                    cmd.Parameters.AddWithValue("@id", userid);
                    cmd.ExecuteNonQuery();
                    con.Close();
                    bind();
                }
            }
        }
    }
    private void chacked()
    {
        for (int i = 0; i < GridView1.Rows.Count; i++)
        {
            CheckBox ckd = (CheckBox)GridView1.Rows[i].FindControl("main");
            //VERIFY IF YOUR CHECKBOX IS NOT NULL
            if (ckd != null)
            {
                ckd.Checked = true;
            }
        }
    }
}

Hope it helps in any way.