Non-invocable member 'File' cannot be used like a method while generating Reports

问题

I used a method for generating report in my previous project and tried to use the same method in the new project. However, I encounter "Non-invocable member 'File' cannot be used like a method" error and File cannot be recognized. By looking at the references of file, it seems to be FileContentResult Controller.File() in the previous project, but System.IO.File() in the new project (even if I remove using System.IO; from the references lines, I encounter "The name 'File' does not exist in the current context" error). Any idea to fix the problem?

public static FileResult GenerateReport()
{
    EmployeeTableAdapter ta = new EmployeeTableAdapter();
    EmployeeDS ds = new EmployeeDS();

    ds.Employee.Clear();
    ds.EnforceConstraints = false;

    ta.Fill(ds.Employee);

    ReportDataSource rds = new ReportDataSource();
    rds.Name = "ReportingDataSet";
    rds.Value = ds.Employee;

    ReportViewer rv = new Microsoft.Reporting.WebForms.ReportViewer();
    rv.ProcessingMode = ProcessingMode.Local;
    rv.LocalReport.ReportPath = System.Web.HttpContext.Current.                                 
        Server.MapPath("~/Reporting/Employee.rdlc");
    rv.LocalReport.EnableHyperlinks = true;
    rv.LocalReport.EnableExternalImages = true;

    // Add the new report datasource to the report.
    rv.LocalReport.DataSources.Add(rds);
    rv.LocalReport.EnableHyperlinks = true;
    rv.LocalReport.Refresh();

    byte[] streamBytes = null;
    string mimeType = "";
    string encoding = "";
    string filenameExtension = "";
    string[] streamids = null;
    Warning[] warnings = null;

    streamBytes = rv.LocalReport.Render("PDF", null, out mimeType, out 
        encoding, out filenameExtension, out streamids, out warnings);

    return File(streamBytes, mimeType, "Application" + "_" + ".pdf");
}

Note: I use MVC5 and SQL Server.

回答1:

System.IO.File is a static helper class for reading/writing files, you can't create an instance of a static class, so you can certainly not return it.

The File you're looking for is a method in the System.Web.MVC namespace which returns a FileContentResult, see here on msdn.

回答2:

Moving the method to the Controller solved the problem. Thanks a lot @AlexanderDerck for your help.

回答3:

You may want to pass an instance of your controller to your method like this

In your controller method

   public async Task<IActionResult> GetFile()
   {
    ...
        return await _fileManager.GetFileAsync(this, "filename", mimeType);
    }

In your other class FileManager

public async Task<FileStreamResult> GetFileAsync(ControllerBase controller, string filename, string mimeType)
    {
        ...
        return controller.File(memory, mimeType, filename);
    }

来源：https://stackoverflow.com/questions/35936628/non-invocable-member-file-cannot-be-used-like-a-method-while-generating-report