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Hello guys , I try to create a Download Manager but when I was running my project and I click in start download button after that this error happen.
______________________________________________________________________________________________________
See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.
************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
at DotnetDownloader.frmnewdownload.btnstartdownload_Click(Object sender, EventArgs e) in E:\VisualProject(CSharp)\DownloadMenager\DotnetDownloader\frmnewdownload.cs:line 72
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
************** Loaded Assemblies **************
mscorlib
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
DotnetDownloader
Assembly Version: 1.0.0.0
Win32 Version: 1.0.0.0
CodeBase: file:----------------------------------------
System.Windows.Forms
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
System
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
System.Drawing
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
System.Configuration
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
System.Core
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
System.Xml
Assembly Version: 4.0.0.0
Win32 Version: 4.7.3056.0 built by: NET472REL1
CodeBase: file:----------------------------------------
************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.
For example:
<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>
When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.
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frmnewdownload.cs:line 72
You want us to guess what's at that line? Need an NDA?
"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal
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E:\VisualProject(CSharp)\DownloadMenager\DotnetDownloader\frmnewdownload.cs:line 72
You have a reference variable at that line which has not been initialised, so is therefore a NullReference.
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Have you tried putting debugger at this line and see why you getting no value?
modified 20-Sep-20 21:01pm.
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I have a tree created at design time with 3 root nodes and 3 levels 3x3x3 =39 nodes as the default.
The nodes can be dynamically recreated.
When I cleared the nodes then recreated them, I tried looping through to add properties to the nodes of each level including their relevant context menu name.
<pre lang="text">
Private Sub RedoTree_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles RedoTree.Click
treeLoad()
treeExecutive.ExpandAll()
restoreTP()
treeExecutive.Nodes(0).EnsureVisible()
End Sub
<pre>
Sub restoreTP() ' renew treenode properties
Dim s As String, l As Short
treeExecutive.Update()
For Each treenode In treeExecutive.Nodes
s = treenode.Name
l = Len(s)
treenode.ForeColor = Color.GhostWhite
If treenode.Text <> s Then treenode.ForeColor = Color.Black
Select Case l
Case 1
treenode.NodeFont = New Font("Arial Rounded MT Bold", 10.8)
treenode.ContextMenuStrip = CMSRoot
Case 2
treenode.NodeFont = New Font("Arial", 10.2)
treenode.ContextMenuStrip = CMSTree
Case Else
treenode.NodeFont = New Font("Arial Narrow", 9)
treenode.ContextMenuStrip = CMSTree
End Select
Next
End Sub
The root nodes are number 1-3, then 11,12,13 .... 111,112,113 Total is 39 nodes
ONLY THE ROOT NODES ARE RECOGNISED AND DEALT WITH.
All the child nodes are ignored as if they don't exist
Am bogged down on this and would appreciate any help 
Demac
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The TreeView's Nodes property[^] only returns the root nodes. Each node has its own Nodes property[^] containing its child nodes.
To iterate through all nodes in the tree, you will need a recursive method. For example:
Sub restoreTP()
treeExecutive.BeginUpdate()
Try
restoreTP(treeExecutive.Nodes)
Finally
treeExecutive.EndUpdate()
End Try
End Sub
Sub restoreTP(ByVal nodes As TreeNodeCollection)
Dim s As String, l As Integer
For Each treenode As TreeNode in nodes
...
restoreTP(treenode.Nodes)
Next
End Sub
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Hi
thx Richard for that info
Not familiar with recursion, but now you've helped me improve my understanding of treeviews.
I did circumvent the problem by updating node properties as they are created.
I can post that code if it might help others.
demac 
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We are writing a combo box custom control using MS text box and list view. We are in a position where we need to provide token (close) option for the options that will be displayed in the combo box? So do you have any suggestion? Refer the below image for better understanding of the requirement.
Google Images[^]
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WinForms or WPF? There's articles on CodeProject for both that show how to draw something as the selected item. Start there 
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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Please do not do this. Post your question in one forum only.
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I'm really sorry, it does not happen again, I was wrong on the topic, that's why I did it
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Hello there. I started learning new c #. I'm doing a project. Similar to devexpress windowsmail. But the designs in my project didn't interfere with the truth. colors, dynamic designs, background colors etc .... How can I design a design like devexpress? it is an eye-catching design wowwwww ..... Please help me please. 
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If you are new to C#, I would wait before I tried to do something more complex like this unless you are a DevExpress customer, in which case, you should have all the sourcecode you need available.
This space for rent
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You're right, Pete. thanks for the advice. to consider
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Hi there
I have two forms called form1 and form2 . In form2 I have 10 trackbar . I want to change values in form1 when I change form2 trackbars . How can i do this ? can i select a void in form1 for form2 trackbars ?
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Can you please send your code? It would be useful to help you.
Thanks.
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Hello all,
I recently installed DNN v9.x on a VM with about 250GB RAM, 36vCPU with Windows 2012 R2 OS. Database is installed on a separate VM with 320 GB RAM, 42vCPU and same OS.
At first when the site was lunched, everything works ok but as the number of users accessing the site increases, the site begin to throw this error "500 - Internal Server Error". This only last for about 5mins after which when the user freshes the site some couple of times, the error disappears.
While this error lasted, utilization across CPU and Memory was around 4%.
Any help will be appreciated.
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The server configurations look ridiculous.
I create anemic VM's starting out to check performance.
You have to "tune" VM's; ISP hosts (including MS) will let you abuse VM's as much as you want. It's a $ to them.
You said your site was "lunched" ... I agree.
"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal
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Check the application event log on the server to find the details of the error.
Without that, anything you do to try to fix the problem will be a blind guess.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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I have 3 DNN webservers behind a Citrix Load Balancer, the load balancer is configured for SSL Offloading.
I discovered that the login link doesn't work anymore. It just refreshes whenever it is clicked. The URL of the login link is: https://test.abc.net/User-Login?returnurl=%2f. The link when clicked supposed to take users to the page where they will login.
When I changed d Citrix load balancer to HTTP, everything works normal. I.e http://test.abc.net/User-Login?returnurl=%2f takes the users to the Login Page.
Any suggestion on how to resolve this issue will be appreciated.
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What does any of this have to do with Windows Forms?
This space for rent
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Hello all, new here. I am trying to learn how to build a Windows GUI program for a few .exe and cmd scripts I have. I started out with WPF but learned I cannot use performance counters with it so I moved on to WinForms. There are alot of video's out there on creating a WinForm for CPU and RAM but I need to create one for a specific NIC with receive bytes, more specifically I would like it to read in Mb. Any help would be greatly appreciated!
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