Insufficient key column information for updating and refreshing
Yet relational databases provide critical infrastructure for long-term storage and query processing, and modern programming languages are indispensable for agile development and rich computation.Until now, it has been the job of the application developer to resolve this mismatch in each application separately.Your application is then free to manipulate the objects while LINQ to SQL stays in the background tracking your changes automatically.Together, the LINQ to SQL run-time infrastructure and design-time tools significantly reduce the workload for the database application developer.
Yet by obscuring the true data source, these solutions end up throwing away the most compelling feature of relational databases; the ability for the data to be queried.
Only instances of classes declared as tables will be stored in the database.
Instances of these types of classes are known as entities.
Objects stand alone, existing as long as they are still referenced by another object.
Rows exist as elements of tables, vanishing as soon as they are removed.