以下文章來源于UP技術(shù)控 ，作者conan5566 
UP技術(shù)控 不止IT 還有生活 背景web上如果圖片不存在一般是打xx，這時候一般都是會設(shè)置默認(rèn)的圖片代替?，F(xiàn)在用中間件的方式實現(xiàn)統(tǒng)一設(shè)置， 一次設(shè)置，全部作用 。 此示例演示如何解決在ASP.NET Core中找不到圖像時設(shè)置默認(rèn)圖像 先決條件實現(xiàn)方式1、Startup 文件 app.UseDefaultImage(defaultImagePath: Configuration.GetSection("defaultImagePath").Value);2、新建類DefaultImageMiddleware using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
namespace conan.Saas.Framework.Middlewares
{
public class DefaultImageMiddleware
{
private readonly RequestDelegate _next;
public static string DefaultImagePath { get; set; }
public DefaultImageMiddleware(RequestDelegate next)
{
this._next = next;
}
public async Task Invoke(HttpContext context)
{
await _next(context);
if (context.Response.StatusCode == 404)
{
var contentType = context.Request.Headers["accept"].ToString().ToLower();
if (contentType.StartsWith("image"))
{
await SetDefaultImage(context);
}
}
}
private async Task SetDefaultImage(HttpContext context)
{
try
{
string path = Path.Combine(Directory.GetCurrentDirectory(), DefaultImagePath);
FileStream fs = File.OpenRead(path);
byte[] bytes = new byte[fs.Length];
await fs.ReadAsync(bytes, 0, bytes.Length);
//this header is use for browser cache, format like: "Mon, 15 May 2017 07:03:37 GMT".
//context.Response.Headers.Append("Last-Modified", $"{File.GetLastWriteTimeUtc(path).ToString("ddd, dd MMM yyyy HH:mm:ss")} GMT");
await context.Response.Body.WriteAsync(bytes, 0, bytes.Length);
}
catch (Exception ex)
{
await context.Response.WriteAsync(ex.Message);
}
}
}
public static class DefaultImageMiddlewareExtensions
{
public static IApplicationBuilder UseDefaultImage(this IApplicationBuilder app, string defaultImagePath)
{
DefaultImageMiddleware.DefaultImagePath = defaultImagePath;
return app.UseMiddleware<DefaultImageMiddleware>();
}
}
}
3、appsettings.json 添加路徑 "defaultImagePath": "wwwroot\\DefaultImage.png", 4、最后在wwwroot放張DefaultImage.png圖片即可 開源地址https://github.com/conanl5566/Sampleproject
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