Troubleshooting Exceptions: System.Data.ConstraintException

Relax or turn off constraints in your DataSets.

You can use the EnforceConstraints property to temporarily turn off constraints while filling tables in a DataSet object.

Make sure you are not trying to assign a value to a primary key field where the primary key already exists in the data table.

If the primary key exists, this exception is thrown.

Clear datasets before loading them from view state.

If there is data in the dataset when you load it, this exception may be thrown.

Tasks

Reference