GetDesigntimeWarnings is called automatically at design time when the adapter page producer is assembling the current version of its HTML form. This gives the dataset adapter an opportunity to add messages to the version of the HTML form that appears at design time, describing problems that you can rectify. 

AWarnings is the design-time warnings object that assembles design-time warning messages that appear in the HTML form. 

If the DataSet property has not been set, GetDesigntimeWarnings adds a message that indicates this omission. If DataSet is set, but the dataset is not active, GetDesigntimeWarnings adds a message that indicates this problem. If DataSet is set, the dataset is active, but you have not specified the key fields that should be used to locate records in that dataset, GetDesigntimeWarnings adds a message indicating this omission. 

DataSet 

Active 

GetKeyFields