dotnet/aspnetcore · error · Error

Cannot create a JSStreamReference from the value

Error message

Cannot create a JSStreamReference from the value '${streamReference}' as it doesn't have a byteLength.

What it means

Thrown by DotNet.createJSStreamReference() when the supplied value is a typed-array-like object (its .buffer is an ArrayBuffer) but its byteLength property is undefined. byteLength is required to tell .NET the stream's size up front.

Solutions

1. Use a standard typed array (Uint8Array, Int32Array) which always carries byteLength.
2. If wrapping custom data, construct a Uint8Array copy: new Uint8Array(yourBytes).
3. Use a Blob if you only have raw bytes: new Blob([data]).

Example fix

// before
const ref = createJSStreamReference({ buffer: someArrayBuffer }); // no byteLength

// after
const ref = createJSStreamReference(new Uint8Array(someArrayBuffer));

function hasByteLength(v) { return v != null && typeof v.byteLength === 'number'; }
if (v.buffer instanceof ArrayBuffer && !hasByteLength(v)) { throw new TypeError('Typed array missing byteLength'); }

function isTypedArrayWithByteLength(v: unknown): v is ArrayBufferView { return v != null && (v as any).buffer instanceof ArrayBuffer && typeof (v as any).byteLength === 'number'; }

try { return DotNet.createJSStreamReference(value); } catch (e) { throw new Error('Pass a standard typed array or Blob for stream references.', { cause: e }); }

When it happens

Trigger: Passing a DataView or typed array whose byteLength has been deleted, or a custom ArrayBufferView-shaped object missing byteLength. Normal Uint8Array/Int32Array/etc. always have byteLength, so this only fires with malformed or polyfilled typed arrays.

Common situations: Using a mock or polyfill that doesn't fully implement the TypedArray spec; passing a hand-rolled object that quacks like an ArrayBufferView but omits byteLength; an older transpiler/runtime stripping the property.

Related errors

• Supplied value is not a typed array or blob.
• Cannot create a JSStreamReference from the value
• Byte array index ' ' does not exist.
• Cannot create a JSObjectReference from the value
• Invalid JS call result type

AI-assisted analysis of dotnet/aspnetcore@3600ca084e (2026-08-11). Data as JSON: /api/errors/cb78c7f74abc13bf. Report an issue: GitHub.

Appendix: source

Thrown at src/JSInterop/Microsoft.JSInterop.JS/src/src/Microsoft.JSInterop.ts:203

   *
   * @param streamReference The ArrayBufferView or Blob used to create the JavaScript stream reference.
   * @returns The JavaScript data reference (this will be the same instance as the given object).
   * @throws Error if the given value is not an Object or doesn't have a valid byteLength.
   */
  export function createJSStreamReference(streamReference: ArrayBuffer | ArrayBufferView | Blob | any): any {
      let length = -1;

      // If we're given a raw Array Buffer, we interpret it as a `Uint8Array` as
      // ArrayBuffers' aren't directly readable.
      if (streamReference instanceof ArrayBuffer) {
          streamReference = new Uint8Array(streamReference);
      }

      if (streamReference instanceof Blob) {
          length = streamReference.size;
      } else if (streamReference.buffer instanceof ArrayBuffer) {
          if (streamReference.byteLength === undefined) {
              throw new Error(`Cannot create a JSStreamReference from the value '${streamReference}' as it doesn't have a byteLength.`);
          }

          length = streamReference.byteLength;
      } else {
          throw new Error("Supplied value is not a typed array or blob.");
      }

      const result: any = {
          [jsStreamReferenceLengthKey]: length
      };

      try {
          const jsObjectReference = createJSObjectReference(streamReference);
          result[jsObjectIdKey] = jsObjectReference[jsObjectIdKey];
      } catch (error) {
          throw new Error(`Cannot create a JSStreamReference from the value '${streamReference}'.`);
      }

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