SQL NULL vs. C#'s System.DBNull.Value: What's the Difference?

The difference between null and System.DBNull.Value in C#

In database retrieval scenarios, it is crucial to understand the difference between null and System.DBNull.Value. Observation shows that when converting a null value to an integer, rdr["Id"] != null returns true and throws an exception, while rdr["Id"] != System.DBNull.Value correctly returns false.

The fundamental difference between null and System.DBNull.Value lies in their definitions. null means a non-reference, an invalid pointer, indicating the lack of a valid object. System.DBNull.Value, on the other hand, is an instance of the System.DBNull class, a singleton that represents a value that does not exist in the database.

Semantically speaking, null represents an invalid reference, while System.DbNull represents a non-existent value. The gap between these two concepts is large and therefore requires different representation methods. This is why the null object pattern is often used, System.DbNull is an example.

In database retrieval scenarios, it is crucial to distinguish between true null values ​​and System.DBNull.Value references. Proper handling of these situations ensures correct data processing and avoids potential anomalies.

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