How do you tell current sharepoint page is in edit/display/other modes?

Microsoft.SharePoint.WebControls.SPControlMode enumeration contains following values:

• Display
• Edit
• Invalid
• New

With following condition, you can check in which mode you are in:

if (SPContext.Current.FormContext.FormMode == Microsoft.SharePoint.WebControls.SPControlMode.Display)

{
// you are in display mode
}