dotnet/wpf · error · ArgumentException

SR.TableCollectionInOtherCollection

Error message

SR.TableCollectionInOtherCollection

What it means

For a TableColumn that is not parented through a DummyProxy, PrivateConnectChild requires the column to have no parent at all; it then attaches it as a logical child of the Owner table. If item.Parent != null the column already belongs to another parent, and ArgumentException (SR.TableCollectionInOtherCollection) is thrown.

Solutions

1. Remove the column from its previous collection (or clear its logical parent) before adding it here
2. Clone or construct a fresh TableColumn per table
3. Audit shared column resources (styles/templates) so only the column object is per-table

Example fix

// before
tableB.Columns.Add(column); // column still in tableA
// after
if (column.Parent is Table t) { t.Columns.Remove(column); }
tableB.Columns.Add(column);

if (col.Parent != null && col.Parent is not DummyProxy) { /* remove from existing parent first */ }

bool IsUnparented(TableColumn col) => col.Parent == null || col.Parent is DummyProxy;

try { table.Columns.Add(col); } catch (ArgumentException) { DetachColumn(col); table.Columns.Add(col); }

When it happens

Trigger: Adding/Inserting a TableColumn whose Parent is neither null nor a DummyProxy — i.e. the column is already in another collection or has a logical parent.

Common situations: Reusing a single TableColumn instance across two tables; moving columns between tables without removal; binding the same column collection instance to multiple tables.

Understand the failure class

Background: "must be a positive integer", "cannot be empty", "invalid argument": how invalid-argument errors work across open-source libraries — this error's family across 33 libraries.

Related errors

• SR.TableCollectionWrongProxyParent
• SR.TableCollectionOutOfRange
• " }} " element found. Expected fixed page element ( }} ).
• ' ' ContentType is not valid.
• ' ' ID is not a valid XSD ID.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/97c616173a2589b5. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/TableColumnCollectionInternal.cs:150

        internal override void PrivateConnectChild(int index, TableColumn item)
        {
            Debug.Assert(item != null && item.Index == -1);
            Debug.Assert(Items[index] == null);

            // If the TItem is already parented correctly through a proxy, there's no need
            // to change parentage.  Otherwise, it should be parented to Owner.
            if (item.Parent is DummyProxy)
            {
                if (LogicalTreeHelper.GetParent(item.Parent) != Owner)
                {
                    throw new System.ArgumentException(SR.TableCollectionWrongProxyParent);
                }
            }
            else
            {
                if (item.Parent != null)
                {
                    throw new System.ArgumentException(SR.TableCollectionInOtherCollection);
                }

                Owner.AddLogicalChild(item);
            }

            // add the item into collection's array
            Items[index] = item;
            item.Index = index;

            // notify the TItem about the change
            item.OnEnterParentTree();
        }

        /// <summary>
        /// Notifies the TItem about the event;
        /// Disconnects the item from the model tree;
        /// Sets the TItem's slot in the collection's array to null.
        /// </summary>

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