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What's new for .NET 7 (Windows Forms .NET)

  • Artikel

This article describes some of the new Windows Forms features and enhancements in .NET 7.

There are a few breaking changes you should be aware of when migrating from .NET Framework to .NET 7. For more information, see Breaking changes in Windows Forms.

High DPI improvements

High DPI rendering with PerMonitorV2 has been improved:

  • Correctly scale nested controls. For example, a button that's in a panel, which is placed on a tab page.

  • Scale Form.MaximumSize and Form.MinimumSize properties based on the current monitor DPI settings for applications that run ApplicationHighDpiMode set to PerMonitorV2.

    In .NET 7, this feature is disabled by default and you must opt in to receive this change. Starting with .NET 8, this feature is enabled by default and you need to opt out of it to revert to the previous behavior.

    To enable feature, set the configProperties setting in runtimeconfig.json:

    {
  "runtimeOptions": {
    "tfm": "net7.0",
    "frameworks": [
        ...
    ],
    "configProperties": {
      "System.Windows.Forms.ScaleTopLevelFormMinMaxSizeForDpi": true,
    }
  }
}

Accessibility improvements and fixes

This release adds further improvements to accessibility, including but not limited to the following items:

Data binding improvements (preview)

While Windows Forms already had a powerful binding engine, a more modern form of data binding, similar to data binding provided by WPF, is being introduced.

The new data binding features allow you to fully embrace the MVVM pattern and the use of object-relational mappers from ViewModels in Windows Forms easier than before. This, in turn, makes it possible to reduce code in the code-behind files, and opens new testing possibilities. More importantly, it enables code sharing between Windows Forms and other .NET GUI frameworks such as WPF, UWP/WinUI, and .NET MAUI. And to clarify a commonly asked question, there aren't any plans to introduce XAML in Windows Forms.

These new data binding features are in preview for .NET 7, and more work on this feature will happen in .NET 8.

To enable the new binding, add the EnablePreviewFeatures setting to your project file. This is supported in both C# and Visual Basic.

<Project Sdk="Microsoft.NET.Sdk">

  <!-- other settings -->

  <PropertyGroup>
    <EnablePreviewFeatures>true</EnablePreviewFeatures>
  </PropertyGroup>

</Project>

The following code snippet demonstrates the new properties, events, and methods added to the various classes in Windows Forms. Even though the following code example is in C#, it also applies to Visual Basic.

public class Control  {
    [BindableAttribute(true)]
    public virtual object DataContext { get; set; }
    [BrowsableAttribute(true)]
    public event EventHandler DataContextChanged;
    protected virtual void OnDataContextChanged(EventArgs e);
    protected virtual void OnParentDataContextChanged(EventArgs e);
}

[RequiresPreviewFeaturesAttribute]
public abstract class BindableComponent : Component, IBindableComponent, IComponent, IDisposable {
    protected BindableComponent();
    public BindingContext? BindingContext { get; set; }
    public ControlBindingsCollection DataBindings { get; }
    public event EventHandler BindingContextChanged;
    protected virtual void OnBindingContextChanged(EventArgs e);
}

public abstract class ButtonBase : Control {
    [BindableAttribute(true)]
    [RequiresPreviewFeaturesAttribute]
    public ICommand? Command { get; set; }
    [BindableAttribute(true)]
    public object? CommandParameter { [RequiresPreviewFeaturesAttribute] get; [RequiresPreviewFeaturesAttribute] set; }
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler? CommandCanExecuteChanged;
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler? CommandChanged;
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler? CommandParameterChanged;
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandCanExecuteChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandParameterChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnRequestCommandExecute(EventArgs e);
}

public abstract class ToolStripItem : BindableComponent, IComponent, IDisposable, IDropTarget {
    [BindableAttribute(true)]
    [RequiresPreviewFeaturesAttribute]
    public ICommand Command { get; set; }
    [BindableAttribute(true)]
    public object CommandParameter { [RequiresPreviewFeaturesAttribute] get; [RequiresPreviewFeaturesAttribute] set; }
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler CommandCanExecuteChanged;
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler CommandChanged;
    [RequiresPreviewFeaturesAttribute]
    public event EventHandler CommandParameterChanged;
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandCanExecuteChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnCommandParameterChanged(EventArgs e);
    [RequiresPreviewFeaturesAttribute]
    protected virtual void OnRequestCommandExecute(EventArgs e);
}

Miscellaneous improvements

Here are some other notable changes:

  • Drag-and-drop handling matches the Windows drag-and-drop functionality with richer display effects such as icons and text labels.
  • Folder and file dialogs allow for more options:
    • Add to recent
    • Check write access
    • Expanded mode
    • OK requires interaction
    • Select read-only
    • Show hidden files
    • Show pinned places
    • Show preview
  • ErrorProvider has a HasErrors property now.
  • Form's snap layout is fixed for Windows 11.

See also