OLE calls require the current thread to be in single-threaded apartment (STA) mode

[patrick]

Hello

Please Help me

I have to use FolderBrowserDialog.
BUT...

Error Message :
System.Threading.ThreadStateException: 'OLE calls require the current thread to be in single-threaded apartment (STA) mode.
Make sure the indicated STAThreadAttribute exists in the Main function.
This exception only occurs when a debugger is attached to the process.
--------------------
I shouldn't use [STAThread] here.

namespace NotSTA
{
    class Program
    {    
        static void Main(string[] args)
        {
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
             Application.Run(new MainForm());               
        }
    }
}
namespace NotSTA
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
            {
                MessageBox.Show(folderBrowserDialog1.SelectedPath);
            }
        }
    }
}

namespace NotSTA
{
    class Program
    {
         [STAThread] //<================ I shouldn't use [STAThread] Here.
        static void Main(string[] args)
        {
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
             Application.Run(new MainForm());               
        }
    }
}

Please Help me

 

[Skydiver]

Why shouldn't you use STA? Most of WinForms code assumes STA.

 

[Skydiver]

If you don't believe me, you can read about it straight from Jessica Fosler who worked on the Windows Shell team:

Why is STAThread required?

learn.microsoft.com

 

[patrick]

If you don't believe me, you can read about it straight from Jessica Fosler who worked on the Windows Shell team:

Why is STAThread required?

learn.microsoft.com

The reason is that the error below appears.

Observer 'ContextSwitchDeadlock' : 'The CLR did not switch from COM context 0x1692530 to COM context 0x1692478 in 60 seconds. The thread that owns the target context/apartment is not handling the pump, it is pumping Windows messages and handling a very long running operation. This situation can even make memory usage an increasing issue, impacting performance and making the application unresponsive for a fraction of the time. To avoid this problem, all Single Threaded Apartment (STA) threads should use a handling primitive (e.g. CoWaitForMultipleHandles) and handle internal handling during long-running operations.'
[STAThread] ---ContextSwitchDeadlock

If you delete [STAThread], the ContextSwitchDeadlock error does not occur.


Managed Debugging Assistants => Uncheck ContextSwitchDeadlock <====I don't want to use this method.

 

[Skydiver]

I suspect that you are not showing us the full code to reproduce that problem. The code from post #1 works without problems for me.

 

[patrick]

I suspect that you are not showing us the full code to reproduce that problem. The code from post #1 works without problems for me.

[ContextSwitchDeadlock] is occurring while uploading large files To FTP.
If you delete [STAThread], [ContextSwitchDeadlock] will not occur.

 

[Skydiver]

Please show minimal code that reproduces the problem.

 

[Skydiver]

[ContextSwitchDeadlock] is occurring while uploading large files To FTP.

If you are doing a large FTP uploads in one of your the click handler, that means that you are doing work on the UI thread. If messages aren't being pumped on the UI thread, then you'll get exactly that error because COM/OLE expects to see messages being pumped because COM/OLE uses the Windows message queue to communicate between the various objects. Recall that COM/OLE was developed before multi-threading and TCP/IP became ubiquitous. And so it's design was based on cooperative multi-tasking, with the Windows message pump being the center of that cooperation.

So don't do your FTP upload on the main UI thread. Instead do it in a background worker thread pool thread. Or make use of async/await if the FTP library you are using supports async. If it doesn't support async, you could do work in a thread pool by using Task.Run().