Display data from database to listview object reference error

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Hello all,
I am using UserControl to use it in panel in the main form, but the main form design crashes when i'm using the code bellow to show data in lostview.
and give me this error
http://store1.up-00.com/2016-08/14726908191.png[^]
The error:

C#

Object reference not set to an instance of an object.

C#

Try
            Conn.Open()
            Dim dt As New DataTable
            Dim ds As New DataSet
            ds.Tables.Add(dt)
            Dim da As New SqlDataAdapter("select * from companies order by sdate DESC", Conn)
            da.Fill(dt)
            Dim myrow As DataRow
            For Each myrow In dt.Rows
                ListView1.Items.Add(myrow.Item(0)).ToString()
                ListView1.Items(ListView1.Items.Count - 1).SubItems.Add(myrow.Item(1))
                ListView1.Items(ListView1.Items.Count - 1).SubItems.Add(myrow.Item(2))
                ListView1.Items(ListView1.Items.Count - 1).SubItems.Add(myrow.Item(3))
                ListView1.Items(ListView1.Items.Count - 1).SubItems.Add(myrow.Item(4))
                ListView1.Items(ListView1.Items.Count - 1).SubItems.Add(myrow.Item(5))
            Next
            Conn.Close()

        Catch ex As SqlException
            MsgBox(ex.Message, MsgBoxStyle.Critical, "SQL Error")
            Conn.Close()
            'Catch ex As Exception
            'MsgBox(ex.Message, MsgBoxStyle.Critical, "General Error")
        End Try

What I have tried:

SO i don't know what i can do to solve this problem
i need your help.

Posted 31-Aug-16 14:53pm

Rabee Qabaha

Updated 31-Aug-16 19:38pm

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1 solution

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OriginalGriff · Accepted Answer · 2016-08-31T19:38:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!

In this specific case it's even worse, because the problem is something to do with the constructor for your control, so it's even difficult to debug. So start by removing all the code from your constructor, and add it back slowly until you control can be displayed. Again, we can't do that for you!

Display data from database to listview object reference error

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Display data from database to listview object reference error

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