Vb net and null

A string in VB. NET can be assigned to Nothing, which is the same concept as Null. We can test a Nothing String with the String. IsNullOrEmpty method. NET program that uses String. Nothing is not just like null in C. Instead, it has a special behavior when used with value types—it acts like the default. Note: Thanks to Matthieu Penant for pointing out that Nothing has a separate meaning on value types.

Quote: In Visual Basic, if you set a variable of a non-nullable value type to Nothing, the variable is set to the default value for its declared type. A reference that points to nothing can cause an Exception. An object may not exist.

A reference may point to nothing. We use the literal Nothing to indicate a null, nil, nonexistent object. We assign to Nothing, test against it, and ponder nothingness. A NullReferenceException is caused by accessing something on a Nothing value. An example. First, this program assigns a String variable to Nothing. This is not an empty string. It is a String object that does not exist. We compare it to Nothing in an If-statement.

A string in VB. NET can be assigned to Nothing, which is the same concept as Null. We can test a Nothing String with the String. IsNullOrEmpty method. Tip The term "null" is simply a different name for "Nothing. NET program that uses String.

Null versus nothing. Nothing is not just like null in C. Instead, it has a special behavior when used with value types—it acts like the default.

Note Thanks to Matthieu Penant for pointing out that Nothing has a separate meaning on value types. Is, IsNot. References can be compared with the "Is" and "IsNot" operators. In VB. Value types cannot be equal to null. But with the Nullable structure, we can wrap an Integer and set it to null with Nothing.

This can help programs be clearer. A summary. Nothing has two meanings. You can update a field to null by setting it to NULL. Chris, Master of All Things Insignificant. NET code, set the field equal to System. You can also check if a value is null using this same object.

I have tried to use that method but variables defined with a date will not accept system. It says that it can not be converted to a date. Cor Ligthert. Lakota, Are you using a datatable or a datareader, probably it is than easier to answer you.

Or maybe even a datatable with binding to a control, what is again a little bit else, where it differs if it is a "datasource" kind of control or a databinding kind of control. Maybe you can tell that? This discussion thread is closed Start new discussion. Similar topics PHP.

Microsoft SQL Server. Help with special values Null, Empty, "", etc. MySQL Database.