app.map .net core

Run

Terminates chain. No other middleware method will run after this. Should be placed at the end of any pipeline.

app.Run(async context =>
{
    await context.Response.WriteAsync("Hello from " + _environment);
});

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Use

Performs action before and after next delegate.

app.Use(async (context, next) =>
{
    //action before next delegate
    await next.Invoke(); //call next middleware
    //action after called middleware
});
Ilustration of how it works: enter image description here

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MapWhen

Enables branching pipeline. Runs specified middleware if condition is met.

private static void HandleBranch(IApplicationBuilder app)
{
    app.Run(async context =>
    {
        await context.Response.WriteAsync("Condition is fulfilled");
    });
}

public void ConfigureMapWhen(IApplicationBuilder app)
{
    app.MapWhen(context => {
        return context.Request.Query.ContainsKey("somekey");
    }, HandleBranch);
}

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Map

Similar to MapWhen. Runs middleware if path requested by user equals path provided in parameter.

private static void HandleMapTest(IApplicationBuilder app)
{
    app.Run(async context =>
    {
        await context.Response.WriteAsync("Map Test Successful");
    });
}

public void ConfigureMapping(IApplicationBuilder app)
{
    app.Map("/maptest", HandleMapTest);

}