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Inserts an item into the collection at the specified index.
protected override void InsertItem(int index, DateField item)Protected Overrides Sub InsertItem(index As Integer, item As DateField)| Type | Name | Description | 
|---|---|---|
| int | index | The zero-based index at which item should be inserted. | 
| DateField | item | The object to insert. | 
| Type | Condition | 
|---|---|
| InvalidOperationException | When add the DateField of the same function to the collection, e.g. the a DateYearField is in the collection, you cannot add either DateEraField or DateEraYearField. |