By default, the HostReadOnly property is exHostReadWrite, which indicates that all operations are allowed. Even so, if the control's data-source does not allow changes, certain operations may be not allowed. 

The HostReadOnly property changes the following properties of the Host:

• ReadOnly property, Retrieves or sets a value that indicates whether the control is read only
• AutoDrag property, Gets or sets a value that indicates the way the component supports the AutoDrag feature
• Chart.AllowCreateBar property, Allows creating new bars using the mouse.
• Chart.BarsAllowSizing property, Specifies whether bars can be resized at run-time.
• Chart.AllowLinkBars property, Specifies whether the user can link the bars using the mouse.

The Error event notifies your application once any error occurs. 

For instance, the following error:

0 The data-source provides no support for AddNew method[...]
0 The data-source provides no support for Delete method[...]
0 The data-source provides no support for Update method[...]

Indicates that no AddNew, Delete or Update is allowed, and so no Save will be performed.

For instance, the the HostReadOnly on exHostReadOnly, makes the control read-only, so no changes are allowed. Even so, you can still change the Host's properties like ReadOnly, AllowCreateBar, to make the control works the way as you desire.