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IFormFile

As explained in ASP.NET Core in Action, 3e

IFormFile is an ASP.NET Core interface representing a file uploaded through an HTTP form, including its metadata and content access.

IFormFile represents a file uploaded through an HTTP form. ASP.NET Core recognizes it as a special binding type and populates it with the uploaded file’s metadata and content access. section 7.6 section 7.6.3

Use the interface to access:

  • FileName, the client-provided filename, which must not be trusted or used directly for storage. section 7.6.3
  • ContentType and Length, which describe the uploaded content. section 7.6.3
  • OpenReadStream(), which provides access to the buffered file contents. section 7.6.3
  • IFormFileCollection, IEnumerable<IFormFile>, or List<IFormFile> when multiple files are accepted. section 7.6.3 section 16.2.2

Minimal API upload parameter

An endpoint can declare IFormFile directly: app.MapGet("/upload", (IFormFile file) => {}); ASP.NET Core binds the uploaded file to the handler parameter. For larger uploads, the default approach can consume memory or disk because the complete file is buffered before the handler receives it; streaming may be necessary instead. section 7.6.3

How ASP.NET Core in Action, 3e covers it

How deep it goes
Explains binding, metadata, stream access, buffering, and security risks, but defers the implementation of streaming large files.
Examples
Uses minimal API parameters, Razor Page handler parameters, multiple-file collections, and an interface member listing.
What it assumes
Teaches file binding through endpoint and page-handler parameters while relying on surrounding model-binding conventions.
What you can do after
Apply it via ASP.NET Core minimal APIs or Razor Pages to receive uploaded files and read their contents.
How it connects
Connects file uploads with model binding, minimal APIs, Razor Pages, IFormFileCollection, and request validation.
Cover of ASP.NET Core in Action, 3e
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of ASP.NET Core in Action, 3e. The section links point to the parts of the book it draws on.