public int DeleteAttachment(
	ItemId id,
	string filenameOrAttachId,
	bool isAttachId,
	bool deleteFirstOccurenceOnly
)

Public Function DeleteAttachment ( 
	id As ItemId,
	filenameOrAttachId As String,
	isAttachId As Boolean,
	deleteFirstOccurenceOnly As Boolean
) As Integer

Parameters

id

Type: ItemId
The ID of the item. Null reference (Nothing in Visual Basic) not allowed.

filenameOrAttachId

Type: SystemString
The filename or string ID of the attachment to delete. Null reference or empty string not allowed.

isAttachId

Type: SystemBoolean
If true, filenameOrAttachId is treated as ID; otherwise, filename.

deleteFirstOccurenceOnly

Type: SystemBoolean
if true, only the first occurrence of the attachment with the given filename will be removed; otherwise, all occurrences. Ignored if filenameOrAttachId is true (multiple attachments cannot have the same ID).

Return Value

The attachment will be deleted permanently.

There can be multiple attachements with the same filename. With this method you can delete them all or only the first one.

Note
The method does not cause an exception in case if no attachment with the given filename or attachment ID is found (you'll simly get zero as the return value). Providing incorrect item ID, however, is considered error.

If you need more sophisticated processing of an item, you can use NativeItem property to access its members and then call UpdateItem(EwsItem) to save the changes to the MS Exchange server.

Note
This method is not implemented in .NET Core. Use DeleteAttachmentAsync(ItemId, String, Boolean, Boolean) instead.

Reference