WebForms Load File

Although MVC is my framework of choice Legacy WebForms applications still exist in the world.

.ASPX file

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<div class="form">
	<div>
		<label>File</label>
		<asp:FileUpload id="FileUploadControl" runat="server" />
	</div>
</div>
<div class="form form-buttons">
	<div>
		<label></label>
		<asp:Button ID="ImportButton" Text="Import" runat="server" OnClick="ImportButton_Click" />
	</div>
</div>

Code Behind

Here _importFromExcelFileService is the injected service.

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ImportButton_Click 

if (!Validation())
	return;
	
var savePath = _importFromExcelFileService.SaveFile(FileUploadControl, Server);

Validation method to separate the concearns using the same _importFromExcelFileService service.

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private bool Validation()
{
	var validationMessage = _importFromExcelFileService.Validate(FileUploadControl);
	if (validationMessage != "")
	{
		Tools.ShowMessage(message, validationMessage, messageType.red);
		return false;
	}
	return true;

Service

Although this did create a dependancys on System.Web.UI.WebControls.FileUpload and System.IO.FileInfo I felt this to be a better design.

Its possible to mock these with SystemWrapper ~ https://stackoverflow.com/questions/1582596/how-do-i-moq-the-system-io-fileinfo-class-or-any-other-class-without-an-inter

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public class ImportFromExcelFileService : IImportFromExcelFileService
{
	private readonly string _allowedExtension = ".xlsx";

	public string SaveFile(FileUpload fileUploadControl, HttpServerUtility server)
	{
		string filename = Path.GetFileName(fileUploadControl.FileName);
		var path = server.MapPath("~/WhyIsThisNotBeingReadFromConfig/Tmp");

		if (!Directory.Exists(path))
			Directory.CreateDirectory(path);

		var savePath = Path.Combine(path, Guid.NewGuid() + filename);
		fileUploadControl.SaveAs(savePath);

		return savePath;
	}

	public string Validate(FileUpload fileUploadControl)
	{
		if (!fileUploadControl.HasFile)
			return "Please select a file.";
		
		// DI -_-
		if (new FileInfo(fileUploadControl.FileName).Extension != _allowedExtension)
			return $"Please supply a file in the format {_allowedExtension}";

		return "";
	}
}