How to Detect That C# Windows Forms Code Is Executed Within Visual Studio

How to detect that C# Windows Forms code is executed within Visual Studio?

Try Debugger.IsAttached or DesignMode property or get ProcessName or a combination, as appropriate

Debugger.IsAttached // or                                       
LicenseUsageMode.Designtime // or 
System.Diagnostics.Process.GetCurrentProcess().ProcessName

Here is a sample

public static class DesignTimeHelper {
    public static bool IsInDesignMode {
        get {
            bool isInDesignMode = LicenseManager.UsageMode == LicenseUsageMode.Designtime || Debugger.IsAttached == true;

            if (!isInDesignMode) {
                using (var process = Process.GetCurrentProcess()) {
                    return process.ProcessName.ToLowerInvariant().Contains("devenv");
                }
            }

            return isInDesignMode;
        }
    }
}

How to tell if .NET code is being run by Visual Studio designer

To find out if you're in "design mode":

• Windows Forms components (and controls) have a DesignMode property.
• Windows Presentation Foundation controls should use the IsInDesignMode attached property.

Detecting design mode from a Control's constructor

You can use the LicenceUsageMode enumeration in the System.ComponentModel namespace:

bool designMode = (LicenseManager.UsageMode == LicenseUsageMode.Designtime);

How to programmatically discover whether the running application is installed?

You can use the ApplicationDeployment.IsNetworkDeployed property. Please note that this only works with ClickOnce installations.

private void CheckApplicationStatus() {
    if (ApplicationDeployment.IsNetworkDeployed) {
        // Do something that needs doing when the application is installed using ClickOnce.
    } else {
        // Do something that needs doing when the application is run from VS.
    }
}

How to execute code in design mode for winforms

As an option to run the code in design mode of a form, you can put the code in base class of the form.

The code which you put in the base class of a form will run in design mode of the inherited form. So if you would like to run a code in design mode of a form, you can create a base form and inherit from that form. Then put your code in the methods of the base form.

Example

1. Add New Item and choose a Form and set the name to MyBaseForm.

2. Paste the following code in MyBaseForm.vb:

   Imports System.ComponentModel
   Public Class MyBaseForm
       Protected Overrides Sub OnSizeChanged(e As EventArgs)
           If DesignMode Then
               Dim s = New Size(My.Computer.Screen.WorkingArea.Width * 0.75,
                                My.Computer.Screen.WorkingArea.Height * 0.75)
               TypeDescriptor.GetProperties(Me)("Size").SetValue(Me, s)
           End If
           MyBase.OnSizeChanged(e)
       End Sub
   End Class
   

3. Build the project.
4. Add New Item and choose a InheritedForm and choose MyBaseForm as the base form.

Can't open design view on Visual Studio 2019 C# Windows Form Application

To check the target framework of your project, you can follow Project -> Properties... Application. And then you can see the target in the page.

If the target is .Net Framework, you can follow the steps provided by Flydog57.

If it is a Windows Forms App(.Net Core), there is no Designer by default.

The .NET Core Windows Forms designer is available with the Visual Studio 16.5 Preview 1. So you can try to update Visual Studio to Visual Studio 16.5 Preview 1 or a later version.

For more details, you can refer to this blog.

Updates to .NET Core Windows Forms designer in Visual Studio 16.5 Preview 1

What files do C# programs execute first?

You can immediately "step into" the executing code by using the Debug menu or pressing F11. This will "break" at the first executable line of code

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