var app = WebApplication.Create();app.MapGet("", async context =>{context.Response.Headers.Append("content-type", "text/html;charset=utf-8");var body = $@"<html><head><link href='https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css' rel='stylesheet' /><style>body {{background-color: #f4f4f4;height: 100vh;display: flex;justify-content: center;align-items: center;}}.upload-container {{background-color: white;padding: 40px;border-radius: 10px;box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);width: 400px;}}.custom-file-input {{cursor: pointer;}}</style></head><body><div class='upload-container'><h1 class='text-center mb-4'>上传文件</h1><form action='Upload' method='post' enctype='multipart/form-data'><div class='form-group'><div class='custom-file'><input type='file' class='custom-file-input' id='customFile' name='file'><label class='custom-file-label' for='customFile'>选择文件</label></div></div><button type='submit' class='btn btn-primary btn-block'>上传</button></form></div><script src='https://code.jquery.com/jquery-3.5.1.slim.min.js'></script><script src='https://cdn.jsdelivr.net/npm/bootstrap@4.5.2/dist/js/bootstrap.bundle.min.js'></script><script>// Update the label of the file input with the selected file name$('.custom-file-input').on('change', function (e) {{var fileName = e.target.files[0].name;$(this).next('.custom-file-label').html(fileName);}});</script></body></html>";await context.Response.WriteAsync(body);});app.MapPost("Upload", async context =>{if (context.Request.HasFormContentType){var form = await context.Request.ReadFormAsync();foreach (var f in form.Files){using (var body = f.OpenReadStream()){var fileName = Path.Combine(app.Environment.ContentRootPath, f.FileName);File.WriteAllBytes(fileName, ReadFully(body));await context.Response.WriteAsync($"上传文件被写入到 {fileName}");}}}await context.Response.WriteAsync("");});app.Run();static byte[] ReadFully(Stream input){byte[] buffer = new byte[16 * 1024];using var ms = new MemoryStream();int read;while ((read = input.Read(buffer, 0, buffer.Length)) > 0){ms.Write(buffer, 0, read);}return ms.ToArray();}
在上面代码中，我们首先从服务器端输出一个HTML的页面，我们基于这个页面上传文件并在服务器端接收文件，我们在服务器中从Request中读取我们的文件，并获取到上传的文件，后续可以根据自己的业务系统来处理。
注意在上传文件时，我们客户端提交表单要以Form的方式去提交(也叫做 multipart/form-data)。
在接收文件时，除了上面方法我们还可以使用模型绑定的方式接收文件，接收多个文件时使用IFormFileCollection类型，接收单个文件时使用IFormFile类型。
源代码地址：
https://github.com/bingbing-gui/AspNetCore-Skill/tree/master/src/aspnetcore-knowledge-point/form-upload-file
