Everyone should know that in ASP.NET MVC, if you call the background controller through Ajax, you can return a JSON object, but you cannot directly return the file (unless you refresh the page, then it is not Ajax), so if you want to use If Ajax generates a file and downloads it, you only need to save the generated file to the server first, and then return the file path through JSON before downloading. Of course, since it is temporarily stored, it needs to be deleted immediately after downloading. Corresponding documents.
The following is an example of how to dynamically generate Excel (I have omitted the specific steps to generate Excel, this is not the focus of this article):
1. First create an Action to generate an Excel file
[HttpPost] public JsonResult ExportExcel() { DataTable dt = DataService.GetData(); var fileName = "Excel_" + DateTime.Now.ToString("yyyyMMddHHmm") + ".xls"; //將生成的文件保存到服務器的臨時目錄里 string fullPath = Path.Combine(Server.MapPath("~/temp"), fileName); using (var exportData = new MemoryStream()) { //如何生成Excel這里就不詳細說明啦,我這里對Excel的操作使用的是 NPOI Utility.WriteDataTableToExcel(dt, ".xls", exportData); FileStream file = new FileStream(fullPath, FileMode.Create, FileAccess.Write); exportData.WriteTo(file); file.Close(); } var errorMessage = "you can return the errors in here!"; //返回生成的文件名 return Json(new { fileName = fileName, errorMessage = "" }); }
2. Create a download application Action
[HttpGet] [DeleteFileAttribute] //Action Filter, 下載完后自動刪除文件,這個屬性稍後解釋 public ActionResult Download(string file) { //到服務器臨時文件目錄下載相應的文件 string fullPath = Path.Combine(Server.MapPath("~/temp"), file); //返回文件對象,這里用的是Excel,所以文件頭使用了 "application/vnd.ms-excel" return File(fullPath, "application/vnd.ms-excel", file); }
3. Since you want to automatically delete the file after downloading, create another Action Filter
public class DeleteFileAttribute : ActionFilterAttribute { public override void OnResultExecuted(ResultExecutedContext filterContext) { filterContext.HttpContext.Response.Flush(); //將當前filter context轉換成具體操作的文件并獲取文件路徑 string filePath = (filterContext.Result as FilePathResult).FileName; //有文件路徑后就可以直接刪除相關文件了 System.IO.File.Delete(filePath); } }
4. Finally add the Ajax calling code in the foreground:
//這里我使用了 blockUI 做loading... $.blockUI({ message: '<h3 id="Please-nbsp-wait-nbsp-a-nbsp-moment">Please wait a moment...</h3>' }); $.ajax({ type: "POST", url: '@Url.Action("ExportExcel","YourController")', //調用相應的controller/action contentType: "application/json; charset=utf-8", dataType: "json", }).done(function (data) { //console.log(data.result); $.unblockUI(); //接收返回的文件路徑,此文件這時已保存到服務器上了 if (data.fileName != "") { //通過調用 window.location.href 直接跳轉到下載 action 進行文件下載操作 window.location.href = "@Url.RouteUrl(new { Controller = "YourController", Action = "Download"})/?file=" + data.fileName; } });

C#.NET is a powerful development platform that combines the advantages of the C# language and .NET framework. 1) It is widely used in enterprise applications, web development, game development and mobile application development. 2) C# code is compiled into an intermediate language and is executed by the .NET runtime environment, supporting garbage collection, type safety and LINQ queries. 3) Examples of usage include basic console output and advanced LINQ queries. 4) Common errors such as empty references and type conversion errors can be solved through debuggers and logging. 5) Performance optimization suggestions include asynchronous programming and optimization of LINQ queries. 6) Despite the competition, C#.NET maintains its important position through continuous innovation.

The future trends of C#.NET are mainly focused on three aspects: cloud computing, microservices, AI and machine learning integration, and cross-platform development. 1) Cloud computing and microservices: C#.NET optimizes cloud environment performance through the Azure platform and supports the construction of an efficient microservice architecture. 2) Integration of AI and machine learning: With the help of the ML.NET library, C# developers can embed machine learning models in their applications to promote the development of intelligent applications. 3) Cross-platform development: Through .NETCore and .NET5, C# applications can run on Windows, Linux and macOS, expanding the deployment scope.

The latest developments and best practices in C#.NET development include: 1. Asynchronous programming improves application responsiveness, and simplifies non-blocking code using async and await keywords; 2. LINQ provides powerful query functions, efficiently manipulating data through delayed execution and expression trees; 3. Performance optimization suggestions include using asynchronous programming, optimizing LINQ queries, rationally managing memory, improving code readability and maintenance, and writing unit tests.

How to build applications using .NET? Building applications using .NET can be achieved through the following steps: 1) Understand the basics of .NET, including C# language and cross-platform development support; 2) Learn core concepts such as components and working principles of the .NET ecosystem; 3) Master basic and advanced usage, from simple console applications to complex WebAPIs and database operations; 4) Be familiar with common errors and debugging techniques, such as configuration and database connection issues; 5) Application performance optimization and best practices, such as asynchronous programming and caching.

C# is widely used in enterprise-level applications, game development, mobile applications and web development. 1) In enterprise-level applications, C# is often used for ASP.NETCore to develop WebAPI. 2) In game development, C# is combined with the Unity engine to realize role control and other functions. 3) C# supports polymorphism and asynchronous programming to improve code flexibility and application performance.

C# and .NET are suitable for web, desktop and mobile development. 1) In web development, ASP.NETCore supports cross-platform development. 2) Desktop development uses WPF and WinForms, which are suitable for different needs. 3) Mobile development realizes cross-platform applications through Xamarin.

The C#.NET ecosystem provides rich frameworks and libraries to help developers build applications efficiently. 1.ASP.NETCore is used to build high-performance web applications, 2.EntityFrameworkCore is used for database operations. By understanding the use and best practices of these tools, developers can improve the quality and performance of their applications.

How to deploy a C# .NET app to Azure or AWS? The answer is to use AzureAppService and AWSElasticBeanstalk. 1. On Azure, automate deployment using AzureAppService and AzurePipelines. 2. On AWS, use Amazon ElasticBeanstalk and AWSLambda to implement deployment and serverless compute.


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