dotnet/wpf · error · ArgumentException

SR.GridCollection_MustBeCertainType…

Error message

SR.GridCollection_MustBeCertainType (ColumnDefinitionCollection, ColumnDefinition)

What it means

ArgumentException from ColumnDefinitionCollection.PrivateValidateValueForRemoval: the value being removed is not a ColumnDefinition, so the removal search guard rejects it before scanning the collection.

Solutions

Remove only ColumnDefinition instances
Cast or resolve the item to a ColumnDefinition before calling Remove

Example fix

// before
columns.Remove(new RowDefinition());
// after
columns.Remove(columns[0]);

Defensive patterns

Strategy: type-guard

Validate before calling

if (item is ColumnDefinition cd && cols.Contains(cd)) cols.Remove(cd);

Type guard

bool IsRemovable(object o) => o is ColumnDefinition cd && cd.Parent == grid;

Try / catch

try { cols.Remove(obj); } catch (ArgumentException) { /* wrong type supplied */ }

Prevention

Pass typed ColumnDefinition references, not objects
Don't rely on Remove for type filtering — filter with OfType<ColumnDefinition>() first
Distinguish 'wrong type' (throws) from 'not present' (returns false)

When it happens

Trigger: Calling grid.ColumnDefinitions.Remove(obj) where obj is not a ColumnDefinition (e.g. a RowDefinition or unrelated object). Note: passing a valid ColumnDefinition that is not in the collection does NOT throw — Remove just returns false.

Common situations: Mixing up RowDefinitions and ColumnDefinitions in removal code; removing items from an untyped data-bound list.

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

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/823ffbbae4aefb65. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/ColumnDefinition.cs:614

            if (item.Parent != null)
            {
                throw new ArgumentException(SR.Format(SR.GridCollection_InOtherCollection, "value", "ColumnDefinitionCollection"));
            }
        }

        /// <summary>
        ///     Throws if value is not something the collection expects.
        ///     Returns true if value belongs to the collection.
        /// </summary>
        private bool PrivateValidateValueForRemoval(object value)
        {
            ArgumentNullException.ThrowIfNull(value);

            ColumnDefinition item = value as ColumnDefinition;

            if (item == null)
            {
                throw new ArgumentException(SR.Format(SR.GridCollection_MustBeCertainType, "ColumnDefinitionCollection", "ColumnDefinition"));
            }

            return (item.Parent == _owner);
        }

        /// <summary>
        ///     Sets the specified DefinitionBase at the specified index;
        ///     Connects the value to the model tree;
        ///     Notifies the DefinitionBase about the event.
        /// </summary>
        /// <remarks>
        ///     Note that the function requires that _item[index] == null and
        ///     it also requires that the passed in value is not included into another ColumnDefinitionCollection.
        /// </remarks>
        private void PrivateConnectChild(int index, DefinitionBase value)
        {
            Debug.Assert(value != null && value.Index == -1);
            Debug.Assert(_items[index] == null);

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