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.
: Libraries like BlazorDownloadFile provide a wrapper for these steps if you prefer a pre-packaged solution. ASP.NET Core Blazor file downloads - Microsoft Learn blazor download file from byte array
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. For very small files or older projects, you
: If you reuse a MemoryStream , ensure stream.Position = 0 before passing it to the DotNetStreamReference , or the browser will receive an empty file. In your component, wrap your byte[] in a
In your component, wrap your byte[] in a MemoryStream and pass it to JavaScript using a DotNetStreamReference .
: 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.
window.downloadFileFromStream = async (fileName, contentStreamReference) => { const arrayBuffer = await contentStreamReference.arrayBuffer(); const blob = new Blob([arrayBuffer]); const url = URL.createObjectURL(blob); const anchorElement = document.createElement('a'); anchorElement.href = url; anchorElement.download = fileName ?? ''; anchorElement.click(); anchorElement.remove(); URL.revokeObjectURL(url); // Cleanup memory } Use code with caution. Step B: C# Razor Component