dotnet/wpf · error · ArgumentException

SR.Collection_BadDestArray

Error message

SR.Collection_BadDestArray

What it means

Model3DCollection.CopyTo catches InvalidCastException from Array.SetValue while copying elements and rethrows it as ArgumentException(SR.Collection_BadDestArray, e) with the collection type name. This happens when the destination array's element type cannot accept a Model3D (e.g. a non-Model3D array passed through the non-generic ICollection.CopyTo).

Solutions

1. Copy into a Model3D[] or a covariantly compatible array (e.g. Model3D[] to object[] with enough capacity).
2. Verify array element type with typeof(Model3D).IsAssignableFrom(array.GetType().GetElementType()) before CopyTo.
3. Inspect the inner InvalidCastException in the ArgumentException for the exact type conflict.

Example fix

// before
var bad = new Visual3D[collection.Count];
((ICollection)collection).CopyTo(bad, 0); // InvalidCastException -> Collection_BadDestArray
// after
var good = new Model3D[collection.Count];
collection.CopyTo(good, 0);

var et = array.GetType().GetElementType();
if (et == null || !typeof(Model3D).IsAssignableFrom(et)) throw new ArgumentException("Destination array element type must be assignable from Model3D.");

bool IsCompatibleDest(Array a) => a?.GetElementType() is Type t && typeof(Model3D).IsAssignableFrom(t);

try { collection.CopyTo(array, index); } catch (ArgumentException ex) when (ex.InnerException is InvalidCastException) { /* use correctly typed array */ }

When it happens

Trigger: Calling the non-generic ICollection.CopyTo with an array of an incompatible element type (e.g. object[] filled with other types is fine, but int[] or Visual[] fails); passing a Model3DCollection's items into a wrongly-typed buffer.

Common situations: Legacy non-generic ICollection-based code paths; reflection or COM interop helpers that treat collections as IList and pass loosely typed arrays.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• SR.Collection_BadDestArray
• SR.Format(SR.Collection_BadDestArray, "Visual3DCollection")
• Cannot pass multidimensional array to the CopyTo method on…
• SR.Argument_InvalidArrayType
• SR.CannotConvertType

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/ebd81c827670bac3. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media3D/Generated/Model3DCollection.cs:427

            if (array.Rank != 1)
            {
                throw new ArgumentException(SR.Collection_BadRank);
            }

            // Elsewhere in the collection we throw an AE when the type is
            // bad so we do it here as well to be consistent
            try
            {
                int count = _collection.Count;
                for (int i = 0; i < count; i++)
                {
                    array.SetValue(_collection[i], index + i);
                }
            }
            catch (InvalidCastException e)
            {
                throw new ArgumentException(SR.Format(SR.Collection_BadDestArray, this.GetType().Name), e);
            }
        }

        bool ICollection.IsSynchronized
        {
            get
            {
                ReadPreamble();

                return IsFrozen || Dispatcher != null;
            }
        }

        object ICollection.SyncRoot
        {
            get
            {
                ReadPreamble();

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