In Blazor, downloading a file from a byte[] requires bridging the gap between C# and the browser's JavaScript environment. While Blazor handles the logic, browsers still rely on a specific JavaScript "anchor click" mechanism to trigger a native download.
: Memory inefficient; Base64 strings are ~33% larger than the original data. C# Implementation:
await JS.InvokeVoidAsync("jsSaveAsFile", "file.txt", Convert.ToBase64String(myByteArray)); Use code with caution. javascript blazor download file from byte array
This guide explores the standard methods for small and large files, including optimized approaches for modern versions of .NET. 1. The Streaming Approach (Recommended)
: For files larger than 250MB, Microsoft recommends downloading directly from a URL via a controller or static file path rather than marshaling bytes through JS interop. In Blazor, downloading a file from a byte[]
For very small files or older projects, you can convert the byte[] directly to a Base64 string and pass it to a JavaScript function that uses a Data URL. : Simplest implementation.
: If you reuse a MemoryStream , ensure stream.Position = 0 before passing it to the DotNetStreamReference , or the browser will receive an empty file. C# Implementation: await JS
For modern Blazor apps (v6.0+), the most efficient way to handle file downloads is via . Instead of converting your byte[] to a massive Base64 string, you can stream it directly to the browser, saving memory and improving performance. Step A: JavaScript Helper