Custom Middlewares in asp.net Core
Middleware in ASP.NET Core is software that's assembled into an application pipeline to handle requests and responses. Custom middleware allows developers to insert their own logic into this pipeline to perform specific tasks, such as logging, error handling, authentication, etc.
To create a custom error handling middleware in ASP.NET Core, we'll write a middleware that catches exceptions thrown during request processing and generates a custom error response.
Here's a step-by-step guide to creating a custom error-handling middleware:
1. Create a Custom Error Handling Middleware
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using System;
using System.Threading.Tasks;public class ErrorHandlingMiddleware
{
private readonly RequestDelegate _next;public ErrorHandlingMiddleware(RequestDelegate next)
{
_next = next;
}public async Task InvokeAsync(HttpContext context)
{
try
{
// Call the next middleware in the pipeline
await _next(context);
}
catch (Exception ex)
{
// Handle the exception and generate a custom error response
await HandleExceptionAsync(context, ex);
}
}private Task HandleExceptionAsync(HttpContext context, Exception exception)
{
// Log the exception (you can use a logging framework like Serilog, NLog, etc.)// Customize the error response
context.Response.ContentType = "application/json";
context.Response.StatusCode = StatusCodes.Status500InternalServerError;
return context.Response.WriteAsync("An unexpected error occurred. Please try again later.");
}
}public static class ErrorHandlingMiddlewareExtensions
{
public static IApplicationBuilder UseErrorHandlingMiddleware(this IApplicationBuilder builder)
{
return builder.UseMiddleware<ErrorHandlingMiddleware>();
}
}
2. Register the Middleware in the Startup.cs
In the Configure method of your Startup.cs, add the following line to register the custom error handling middleware:
public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
// ... other middleware registrations app.UseErrorHandlingMiddleware(); // ... other middleware registrations
}
3. Usage
Now, any unhandled exceptions that occur during request processing will be caught by the custom error handling middleware, and an appropriate error response will be generated.
public class HomeController : Controller
{
public IActionResult Index()
{
// Simulate an exception
throw new Exception("This is a sample exception.");
}
}
In this example, when an exception is thrown in the Index action of the HomeController, the custom error handling middleware will catch it and return a customized error response to the client.
Make sure to replace the error response in the HandleExceptionAsync method with a meaningful and appropriate error message or response format based on your application's requirements.
In SQL Server, a trigger is a special type of stored procedure that is automatically executed in response to a specific event, such as an INSERT, UPDATE, or DELETE operation on a table. Triggers are used to enforce business rules, maintain data integrity, and automate certain tasks when changes are made to the data in a table. SQL Server supports two main types of triggers:
➡ DML Triggers (Data Modification Language Triggers):
➡ DML triggers are fired in response to data modification operations, such as INSERT, UPDATE, or DELETE operations on a table. There are two types of DML triggers:
➡ AFTER Trigger (FOR/AFTER INSERT, UPDATE, DELETE): These triggers are executed after the data modification operation is completed. They are often used for auditing or logging changes.
➡ INSTEAD OF Trigger (INSTEAD OF INSERT, UPDATE, DELETE): These triggers replace the original data modification operation. They are often used for handling complex data validation or data transformation.
Here’s an example of a simple AFTER INSERT trigger:
CREATE TRIGGER trgAfterInsert
ON YourTable
AFTER INSERT
AS
BEGIN
— Trigger logic here
END;
➡ DDL Triggers (Data Definition Language Triggers):
➡ DDL triggers are fired in response to data definition language operations, such as CREATE, ALTER, or DROP statements. They are used to monitor and control changes to the database schema and server-level events.
Here’s an example of a DDL trigger:
CREATE TRIGGER ddlTrigger
ON DATABASE
FOR CREATE_TABLE
AS
BEGIN
— Trigger logic here
END;
➡ Triggers can be used to perform various tasks, such as:
Enforcing referential integrity by checking and blocking invalid data modifications.
➡ Logging changes to a table for auditing purposes.
➡ Automatically updating related records in other tables.
Restricting certain data modification operations based on business rules.
Handling complex data transformation or validation before saving data to the database.
➡ It’s important to be cautious when using triggers because they can introduce complexity to the database schema and may impact performance if not used carefully. Make sure that triggers are well-documented and thoroughly tested to ensure they function correctly and efficiently in your database environment.