使用ASP.NET Core下载文件

Question

I´m trying to download a excel file after the file is created and I´m having the following error:

UnauthorizedAccessException: Access to the path 'C:\\Users\\user_name\\Documents\\Visual Studio 2015\\Projects\\Project_Name\\src\\Project_Name\\wwwroot' is denied.

The file is created successfully, the problem is in the download method.

I already try to solve this error doing the following actions:

• Open VS as Admin
• Add IIS_IUSR user to the project folder

Here´s the code:

    private readonly IHostingEnvironment _hostingEnvironment;
    public EmployeeController(ApplicationDbContext context, IHostingEnvironment hostingEnvironment)
    {
        _hostingEnvironment = hostingEnvironment;
    }
    public void createFile()
    {
        string wwwrootPath = _hostingEnvironment.WebRootPath;
        string fileName = @"Employees.xlsx";
        FileInfo file = new FileInfo(Path.Combine(wwwrootPath, fileName));

        if (file.Exists)
        {
            file.Delete();
            file = new FileInfo(Path.Combine(wwwrootPath, fileName));
        }
        using (ExcelPackage package = new ExcelPackage(file))
        {
            ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Employee");
            worksheet.Cells[1, 1].Value = "ID";
            worksheet.Cells[1, 2].Value = "Name";
            worksheet.Cells[1, 3].Value = "Gender";
            worksheet.Cells[1, 4].Value = "Salary (in $)";

            worksheet.Cells["A2"].Value = 1000;
            worksheet.Cells["B2"].Value = "Jon";
            worksheet.Cells["C2"].Value = "M";
            worksheet.Cells["D2"].Value = 5000;

            worksheet.Cells["A3"].Value = 1001;
            worksheet.Cells["B3"].Value = "Graham";
            worksheet.Cells["C3"].Value = "M";
            worksheet.Cells["D3"].Value = 10000;

            worksheet.Cells["A4"].Value = 1002;
            worksheet.Cells["B4"].Value = "Jenny";
            worksheet.Cells["C4"].Value = "F";
            worksheet.Cells["D4"].Value = 5000;

            package.Save(); 
            downloadFile(wwwrootPath);

        }  

}
    public FileResult downloadFile(string filePath)
    {
        var mimeType = "application/vnd.ms-excel";
        FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);

        return File(fileStream, mimeType, "Employees.xlsx");
    }

Note: I didn´t make the deploy of the project in IIS.

Best Regards

Answer 1

In ASP.NET Core you should use PhysicalFileProvider class to access the actual system's files. If you look into File providers section in the documentation:

The PhysicalFileProvider provides access to the physical file system. It wraps the System.IO.File type (for the physical provider), scoping all paths to a directory and its children. This scoping limits access to a certain directory and its children, preventing access to the file system outside of this boundary.

The following should work for you:

string wwwrootPath = _hostingEnvironment.WebRootPath;
string fileName = @"Employees.xlsx";

IFileProvider provider = new PhysicalFileProvider(wwwrootPath);
IFileInfo fileInfo = provider.GetFileInfo(fileName);
var readStream = fileInfo.CreateReadStream();

// PhysicalFileProvider.GetFileInfo returns instance of PhysicalFileInfo that provides implementation of IFileInfo.CreateReadStream method.

Answer 2

I test your code and the error is gone, but the file is not being downloaded. Here is the code:

public FileResult downloadFile(string filePath, string fileName)
{
        IFileProvider provider = new PhysicalFileProvider(filePath);
        IFileInfo fileInfo = provider.GetFileInfo(fileName);
        var readStream = fileInfo.CreateReadStream();
        var mimeType = "application/vnd.ms-excel";
        return File(readStream, mimeType, fileName);
}

Best Regards

Answer 3

I noticed two situations in my code. 1 - If I call the download method directly in my button the download happens, but the file is stored in localhost directory, something like http://localhost:3724/Area/Controller/downLoadMethod . I want the browser to open de download box and then I choose the place to store the file.

2 - If in my button I call the exportMethod and inside of the exportMethod I call the downloadMethod after the file is exported I just get a blank page, the download does't happen.

Best Regards