dotnet/wpf · error · InvalidOperationException

SR.Freezable_CantFreeze

Error message

SR.Freezable_CantFreeze

What it means

Freezable.Freeze() makes the object immutable, but only if every part of the object graph is freezable (CanFreeze is true — no databound or mutable sub-objects remain). The public Freeze() first checks CanFreeze and throws InvalidOperationException(SR.Freezable_CantFreeze) when the check fails, guaranteeing the freeze operation will succeed before mutating state.

Solutions

1. Check CanFreeze before calling Freeze and skip/clone the object when it returns false
2. Remove or replace non-freezable members (Bindings, DynamicResource references, animated values) with fixed values
3. Use GetAsFrozen/GetCurrentValueAsFrozen appropriately and handle the failure path
4. Clone the Freezable and simplify it until CanFreeze returns true

Example fix

// before
brush.Freeze(); // throws if animated
// after
if (brush.CanFreeze) brush.Freeze();
else { var frozen = brush.GetCurrentValueAsFrozen() as SolidColorBrush; }

if (freezable.CanFreeze) freezable.Freeze(); else { /* clone/simplify first */ }

static bool CanSafelyFreeze(System.Windows.Freezable f) => f.CanFreeze && !f.IsFrozen;

try { obj.Freeze(); }
catch (InvalidOperationException ex) { log.Warn($"{obj} cannot be frozen: {ex.Message}"); }

When it happens

Trigger: Calling Freeze() (or GetAsFrozen) on a Freezable whose CanFreeze is false — e.g. a Brush or Geometry containing non-frozen sub-objects, an animation with unresolved bindings, or a Freezable still registered to change handlers.

Common situations: Freezing a SolidColorBrush whose Color is animated, a Pen referencing a non-freezable brush, or any resource defined in XAML with DynamicResource/Binding inside; attempting to freeze resources for cross-thread sharing in performance work.

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

• SR.Format(SR.CrossThreadAccessOfUnshareableFreezable…
• SR.Format(SR.Freezable_CantBeFrozen, GetType().FullName)
• SR.Freezable_AttemptToUseInnerValueWithDifferentThread
• ElementNotAvailableException
• IAnimatable_CantAnimateSealedDO

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/003fb3b5c69d8781. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/Windows/Freezable.cs:172

            get
            {
                return IsFrozenInternal || FreezeCore(isChecking: true);
            }
        }

        /// <summary>
        /// Does an in-place modification to make the object frozen. It is legal to
        /// call this on values that are already frozen.
        /// </summary>
        /// <exception cref="System.InvalidOperationException">This exception
        /// will be thrown if this Freezable can't be frozen. Use
        /// the CanFreeze property to detect this in advance.</exception>
        public void Freeze()
        {
            // Check up front that the operation will succeed before we begin.
            if (!CanFreeze)
            {
                throw new InvalidOperationException(SR.Freezable_CantFreeze);
            }

            Freeze(isChecking: false);
        }

        #endregion

        #region Public Properties

        //------------------------------------------------------
        //
        //  Public Properties
        //
        //------------------------------------------------------

        /// <summary>
        /// Returns whether or not the Freezable is modifiable.  Attempts
        /// to set properties on an IsFrozen value result

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