What causes "SR.Image_OnlyOneInit" in dotnet/wpf?

Create a new BitmapImage instance for each image instead of re-initializing an existing one

dotnet/wpf · error · InvalidOperationException

SR.Image_OnlyOneInit

Error message

SR.Image_OnlyOneInit

What it means

ISupportInitialize.BeginInit on BitmapCacheFile/BitmapInitialize types may only be called once per object; WPF deliberately forbids re-initialization. Calling BeginInit after the object has already been initialized throws InvalidOperationException with SR.Image_OnlyOneInit.

Solutions

Create a new BitmapImage instance for each image instead of re-initializing an existing one
Track initialization with a bool flag so BeginInit is only invoked once per instance
If the URI changes, assign a fresh object or use the Freezable Clone pattern instead of re-running BeginInit

Example fix

// before
if (_bitmap == null) { _bitmap = new BitmapImage(); _bitmap.BeginInit(); }
_bitmap.BeginInit(); // throws on reuse
// after
_bitmap = new BitmapImage();
_bitmap.BeginInit();
_bitmap.UriSource = new Uri(path);
_bitmap.EndInit();

Defensive patterns

Strategy: validation

Validate before calling

bool canBeginInit(BitmapImage img) => img is { } && !_initializedImages.Contains(img); // track instances you already initialized
class InitTracker { private static readonly HashSet<BitmapImage> Done = new(); public static bool IsNew(BitmapImage i) => Done.Add(i); }

Type guard

bool IsReusableImage(BitmapImage img) => img == null; // BitmapImage is single-init: treat as non-reusable, always create new

Prevention

Treat BitmapImage as single-use: create a new instance per image load
Never share one BitmapImage across multiple loads or data items
Centralize image creation in a factory method so BeginInit is called exactly once

When it happens

Trigger: Calling BeginInit() a second time on the same BitmapImage (or other IBitmapInitialize implementer) after a prior BeginInit/EndInit cycle has completed (IsInitAtLeastOnce == true).

Common situations: Reusing a cached BitmapImage instance to load a new URI; loops that reconfigure one shared image object per item; copy-pasted init code running twice for the same instance.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/4fbafe555180b826. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Imaging/BitmapInitialize.cs:21

using System.ComponentModel;

namespace System.Windows.Media.Imaging
{
    #region BitmapInitialize
    /// <summary>
    /// Utility class providing support for ISupportInitialize
    /// </summary>
    internal class BitmapInitialize : ISupportInitialize
    {
        public BitmapInitialize()
        {
        }

        public void BeginInit()
        {
            if (IsInitAtLeastOnce)
                throw new InvalidOperationException(SR.Format(SR.Image_OnlyOneInit, null));

            if (IsInInit)
                throw new InvalidOperationException(SR.Format(SR.Image_InInitialize, null));

            _inInit = true;
        }

        public void EndInit()
        {
            if (!IsInInit)
                throw new InvalidOperationException(SR.Format(SR.Image_EndInitWithoutBeginInit, null));

            _inInit = false;
            _isInitialized = true;
        }

        public void SetPrologue()
        {

View on GitHub (pinned to 81131a70a4)