PrismCommands.Fody is a Fody plugin that provides a simple way to replace methods with Prism DelegateCommand properties at compile time.
This is useful when using the Prism library to build applications with the Model-View-ViewModel (MVVM) architecture. DelegateCommand is a class provided by Prism that implements the ICommand interface and allows you to bind a command from the view to a method in the view model.
- Install the
PrismCommands.FodyNuGet package in your project. - Add
<PrismCommands />to yourFodyWeavers.xmlfile in the project's root directory. This step is necessary for Fody to enable thePrismCommands.Fodyplugin during the build process. - Add a
[DelegateCommand]attribute to any method in your code that you want to replace with a DelegateCommand property. - Build your project. The methods with the
[DelegateCommand]attribute will be replaced with DelegateCommand properties.
public class MyViewModel
{
[DelegateCommand]
public void DoSomething()
{
// Do something here.
}
[DelegateCommand]
public void DoSomethingWithArg(string arg)
{
// Do something with arg here.
}
}After building, each method marked with the [DelegateCommand] attribute will be replaced with a corresponding DelegateCommand property named using the "{MethodName}Command" pattern.
For example, if you have a MyViewModel class with methods named DoSomething and DoSomethingWithArg marked with the [DelegateCommand] attribute, after building, these methods will be replaced with properties named DoSomethingCommand and DoSomethingWithArgCommand.
public class MyViewModel
{
public DelegateCommand DoSomethingCommand { get; }
public DelegateCommand<string> DoSomethingWithArgCommand { get; }
public MyViewModel()
{
DoSomethingCommand = new DelegateCommand(DoSomething);
DoSomethingWithArgCommand = new DelegateCommand<string>(DoSomethingWithArg);
}
private void DoSomething()
{
// Do something here.
}
private void DoSomethingWithArg(string arg)
{
// Do something with arg here.
}
}Thus, you can use the DoSomethingCommand and DoSomethingWithArgCommand properties to bind the commands to the view.
Note that if you have a method with a name that matches the property name created by PrismCommands.Fody, this can lead to conflicts and build errors. To avoid this, avoid using strings in method names that match the "Command" string.
PrismCommands.Fody also supports CanExecute methods for DelegateCommands. To use this feature, create a private method that returns a boolean value and follows the naming convention Can{CommandMethodName}. For example, if your command method is named DoSomething, the corresponding CanExecute method should be named CanDoSomething. The plugin will automatically detect the method if it follows this naming convention.
You can customize the naming pattern for CanExecute methods by adding the CanExecuteMethodPattern attribute to your FodyWeavers.xml file.
For example, to change the pattern to Is{CommandMethodName}Allowed, add the following line to your FodyWeavers.xml file:
<PrismCommands CanExecuteMethodPattern="Is{0}Allowed" />Here's an example of how to use the CanExecute method feature:
public class MyViewModel
{
[DelegateCommand]
public void DoSomething()
{
// Do something here.
}
private bool CanDoSomething()
{
// Return true if the DoSomething command can be executed, false otherwise.
return true;
}
}After building, the DoSomething method will be replaced with a DelegateCommand property named DoSomethingCommand, which will be associated with the CanDoSomething method for its CanExecute logic.
public class MyViewModel
{
public DelegateCommand DoSomethingCommand { get; }
public MyViewModel()
{
DoSomethingCommand = new DelegateCommand(DoSomething, CanDoSomething);
}
private void DoSomething()
{
// Do something here.
}
private bool CanDoSomething()
{
// Return true if the DoSomething command can be executed, false otherwise.
return true;
}
}Now, the DoSomethingCommand property can be used to bind the command to the view, and the CanExecute logic will be taken into account when determining whether the command can be executed or not.
PrismCommands.Fody uses the Mono.Cecil library to modify the assembly at compile time. It scans the assembly for methods with the [DelegateCommand] attribute and replaces them with DelegateCommand properties.
The implementation details can be found in the ModuleWeaver class.
Here are some future plans for PrismCommands.Fody:
- Improve performance and efficiency. As
PrismCommands.Fodyuses the Mono.Cecil library to modify the assembly at compile time, there is some overhead involved in the build process. In the future, we plan to investigate ways to improve the performance and efficiency of the plugin to minimize build times. - Expand documentation and examples. We plan to provide more examples and documentation to help users understand how to use the plugin effectively, as well as showcase some best practices for building Prism applications with the MVVM architecture.
If you have any suggestions or feature requests, feel free to open an issue or contribute to the project!
Contributions are welcome! If you find a bug or have a feature request, please open an issue. If you want to contribute code, please fork the repository and submit a pull request.
Please read the CONTRIBUTING.md file before contributing.
PrismCommands.Fody is licensed under the MIT License.
The following individuals have contributed to the development and maintenance of PrismCommands.Fody:
- Vitaly Kuzyaev (@vitkuz573): Developer of the plugin. Implemented the core functionality of the plugin, wrote the initial codebase, and provided ongoing maintenance and support.
- OpenAI ChatGPT (@openai/chatgpt): Provided assistance with code development and readme composition. Helped with code review, testing, and provided feedback and suggestions for improving the documentation and user experience.
