Introduction to Middleware
Middleware is a component that is assembled into the application pipeline to handle requests and responses.
Middlewares are chained one-after-other and execute in the same sequence how they’re added.
Middleware can be a request delegate (anonymous method or lambda expression) [or] a class.
Middleware - Run
app.Run( )
The extension method called “Run” is used to execute a terminating / short-circuiting middleware that doesn’t forward the request to the next middleware.
app.Run(async (HttpContext context) =>
{
//code
});Middleware Chain
app.Use( )
The extension method called “Use” is used to execute a non-terminating / short-circuiting middleware that may / may not forward the request to the next middleware.
app.Use(async (HttpContext context, RequestDelegate next) =>
{
//before logic
await next(context);
//after logic
});Middleware Class
Middleware class is used to separate the middleware logic from a lambda expression to a separate / reusable class.
class MiddlewareClassName : IMiddleware
{
public async Task InvokeAsync(HttpContext context, RequestDelegate next)
{
//before logic
await next(context);
//after logic
}
}
app.UseMiddleware<MiddlewareClassName>();Middleware Extensions
Middleware extension method is used to invoke the middleware with a single method call.
class MiddlewareClassName : IMiddleware
{
public async Task InvokeAsync(HttpContext context,RequestDelegate next)
{
//before logic
await next(context);
//after logic
}
});
static class ClassName
{
public static IApplicationBuilder ExtensionMethodName(this IApplicationBuilder app)
{
return app.UseMiddleware<MiddlewareClassName>();
}
}
app.ExtensionMethodName();Conventional Middleware
_next = next;
class MiddlewareClassName
{
private readonly RequestDelegate _next;
public MiddlewareClassName(RequestDelegate next)
{
}
public async Task InvokeAsync(HttpContext context)
{
//before logic
await _next(context);
//after logic
}
});
static class ClassName
{
public static IApplicationBuilder ExtensionMethodName(this IApplicationBuilder app)
{
return app.UseMiddleware<MiddlewareClassName>();
}
}
app.ExtensionMethodName();The Right Order of Middleware
app.UseExceptionHandler("/Error");
app.UseHsts();
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseCors();
app.UseAuthentication();
app.UseAuthorization();
app.UseSession();
app.MapControllers();
//add your custom middlewares
app.Run();Middleware - UseWhen
app.UseWhen( )
The extension method called “UseWhen” is used to execute a branch of middleware only when the specified condition is true.
app.UseWhen(
context => { return boolean; },
app =>
{
//add your middlewares
}
);