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Static Command Services

This feature is new in DotVVM 2.0.

Static Command Services is a feature which allows injecting of a C# class in the page using @service directive and calling its methods using Static Command Binding. This allows to use static command binding on instance methods and using dependency injection.

Service Registration

First, make sure that the service is registered in IServiceCollection. This can be done in DotvvmStartup.cs:

public void ConfigureServices(IDotvvmServiceCollection options)
{
    ...

    options.Services.AddSingleton<CalculatorService>();
}

To register a static command service, add the following directive at the top of the page:

@service _calculator = MyApp.Services.CalculatorService

This will create a variable called _calculator which you can use in binding expressions in the page.

If you prefer to use an interface in the view, it is possible - just make sure that it is correctly registered in IServiceCollection and that the implementation type or a factory method is provided:

options.Services.AddScoped<ICalculationService, CalculationService>();

You can use any lifetime policy supported by IServiceProvider: Singleton, Scoped and Transient.

Using Static Command Services

You can call any method marked with [AllowStaticCommand] attribute using static command binding. Optionally, you can assign the return value to any property in the viewmodel:

<dot:Button Text="Calculate" Click="{staticCommand: Result = _calculator.Calculate(Number1, Number2)}" />

The Calculate method is defined like this:

public class CalculatorService
{

    public CalculatorService(/* you can specify any dependencies - they will be resolved using IServiceProvider */ )
    {
    }

    [AllowStaticCommand]
    public int Calculate(int number1, int number2) 
    {
        return number1 + number2;
    }

}

When the button is clicked, DotVVM will send only the identification of the static command and values of Number1 and Number2 properties in the viewmodel. The viewmodel itself is not transferred to the server.

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