How to inherit form in .net design time (there is no inheritance picker)?

Slobodan Krejaković 41

How can I correctly inherit from some template form at design time in VS, on .net?

In .net framework there was Inheritance Picker but I do not find it in .net 8.0.

When I create simple inheritance from another form, like this:

public partial class InheritedForm : BaseForm
{
    public InheritedForm()
    {
        InitializeComponent();
    }
}

I get errors when trying to show Designer:

User's image

KOZ6.0 6,580 Reputation points

2024-06-23T15:05:45.6966667+00:00

Have you built a project that includes BaseForm? If the build is successful, simply create a Form class and modify the inheritance source (Form) to BaseForm.
Slobodan Krejaković 41 Reputation points

2024-06-23T16:05:54.49+00:00

Yes, I did build.... and forms are even in the same project.
KOZ6.0 6,580 Reputation points

2024-06-23T18:15:23.2333333+00:00

What does BaseForm do? Can you provide code?

Slobodan Krejaković 41

Basically I would like to create a base form which saves the form size, state and position to the application settings.

public partial class BaseForm : Form
{
    protected const string LocationSufix = "_Location";
    protected const string SizeSufix = "_Size";
    protected const string WindowStateSufix = "_WindowState";
    protected string SettingsKeyPrefix { get; } = string.Empty;
    public BaseForm()
    {
        InitializeComponent();
        Font = Properties.App.Default.UiFont;
        Load += (s, e) => SetAll();
        LocationChanged += (s, e) => SaveAll();
        SizeChanged += (s, e) => SaveAll();
    }
    private void SetAll()
    {
        SetFormSize();
        SetFormLocation();
        SetWindowState();
    }
    private void SaveAll()
    {
        if (WindowState == FormWindowState.Maximized)
        {
            SaveWindowState();
        }
        else if (WindowState == FormWindowState.Normal)
        {
            SaveFormLocation();
            SaveFormSize();
            SaveWindowState();
        }
    }
    public void SetFormLocation()
    {
        if (StartPosition == FormStartPosition.Manual)
        {
            if (Properties.App.Default[$"{SettingsKeyPrefix}{LocationSufix}"] is not null and Point p)
            {
                Location = p;
            }
        }
    }
    public void SaveFormLocation()
    {
        if (StartPosition == FormStartPosition.Manual && Properties.App.Default[$"{SettingsKeyPrefix}{LocationSufix}"] is not null and Point p && !Location.Equals(p))
        {
            Properties.App.Default[$"{SettingsKeyPrefix}{LocationSufix}"] = p;
            Properties.App.Default.Save();
        }
    }
    public void SetFormSize()
    {
        if (!AutoSize)
        {
            if (Properties.App.Default[$"{SettingsKeyPrefix}{SizeSufix}"] is not null and Size s && s.Height > 0 && s.Width > 0)
            {
                Size = s;
            }
        }
    }
    public void SaveFormSize()
    {
        if (!AutoSize && Properties.App.Default[$"{SettingsKeyPrefix}{SizeSufix}"] is not null and Size s && !Size.Equals(s))
        {
            Properties.App.Default[$"{SettingsKeyPrefix}{SizeSufix}"] = s;
            Properties.App.Default.Save();
        }
    }
    public void SetWindowState()
    {
        if (Properties.App.Default[$"{SettingsKeyPrefix}{WindowStateSufix}"] is not null and FormWindowState s)
        {
            WindowState = s;
        }
    }
    public void SaveWindowState()
    {
        if (Properties.App.Default[$"{SettingsKeyPrefix}{WindowStateSufix}"] is not null and FormWindowState s && s != FormWindowState.Minimized)
        {
            Properties.App.Default[$"{SettingsKeyPrefix}{WindowStateSufix}"] = s;
            Properties.App.Default.Save();
        }
    }
}

KOZ6.0 6,580

How about changing SetAll/SaveAll as follows?

private void SetAll() {
    if (!DesignMode) {
        SetFormSize();
        SetFormLocation();
        SetWindowState();
    }
}
private void SaveAll() {
    if (!DesignMode) {
        if (WindowState == FormWindowState.Maximized) {
            SaveWindowState();
        } else if (WindowState == FormWindowState.Normal) {
            SaveFormLocation();
            SaveFormSize();
            SaveWindowState();
        }
    }
}

What kind of class is Properties?

Slobodan Krejaković 41 Reputation points

2024-06-24T06:02:33.65+00:00

No, still get the same error...

Properties is the standard Settings file:

My idea is to enable prefix for any inherited form, and then the form size, location and state should be picked up from App.settings by using the name pattern.
KOZ6.0 6,580 Reputation points

2024-06-24T07:35:25.4966667+00:00
BaseForm constructor like this:

public BaseForm() { InitializeComponent(); MessageBox.Show("A"); Font = Properties.App.Default.UiFont; MessageBox.Show("B"); Load += (s, e) => SetAll(); LocationChanged += (s, e) => SaveAll(); SizeChanged += (s, e) => SaveAll(); }

When the InheritedForm is displayed in the designer, does it display "A" and "B"? (The displayed message box window may be on the back side of Visual Studio.)
KOZ6.0 6,580 Reputation points

2024-06-24T07:52:54.17+00:00

Debugging Visual Studio with Visual Studio (attach to devenv.exe) may help you catch the error factor.

https://learn.microsoft.com/en-us/visualstudio/debugger/attach-to-running-processes-with-the-visual-studio-debugger?view=vs-2022
Slobodan Krejaković 41 Reputation points

2024-06-24T11:39:59.5866667+00:00

OK, when I comment out this line with setting of Font from Properties, the designer of Inherited form is shown... It seems that the problem is somehow related to usage of Properties.Settings file in the base form...

1 answer

KOZ6.0 6,580 Reputation points

2024-06-24T12:45:58.06+00:00

The form designer executes the constructor of the inherited source and calls the InitializeComponent method.

When designing BeseForm, the constructor of BaseForm is not executed; the constructor of BaseForm is executed when designing InheritedForm.

When saving System.Drawing.Font in the Settings file, set as follows.
Please sign in to rate this answer.
Slobodan Krejaković 41 Reputation points

2024-06-24T17:44:10.95+00:00

I get that, this is how it is already defined at my settings file (App.settings).

What I do not get still, is why would this setting of Font property on the BaseForm crash the designer of the Inherited Form?

If I would like to implement the Font from the BaseForm, also in all inherited forms...

KOZ6.0 6,580 Reputation points

2024-06-24T21:50:16.3733333+00:00

Verdana; 9pt ?

They are separated by semicolons, but in my environment they are separated by commas.

Press "..." button on the far right to display the font dialog.

Can Properties.App.Default.UiFont get a value?

Slobodan Krejaković 41 Reputation points

2024-06-25T05:22:02.3466667+00:00

Yes it can, that is actually how I set it in the first place, I did not type manually. Semicolon is the system separator on my machine, not comma.

KOZ6.0 6,580 Reputation points

2024-06-25T08:33:31.68+00:00

This is all I can tell from the conditions you have presented.

In my environment, I am able to display InheritedForm in the designer even after changing the font.
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.

Share via

How to inherit form in .net design time (there is no inheritance picker)?

1 answer

Your answer