Null is not the same as Empty , which indicates that a variable has not yet been initialized. It is also not the same as a zero-length string "" , which is sometimes referred to as a null string. Use the IsNull function to determine whether an expression contains a Null value.
This is because any expression containing a Null is itself Null and therefore False. This example uses the IsNull function to determine if a variable contains a Null.
Have questions or feedback about Office VBA or this documentation? Please see Office VBA support and feedback for guidance about the ways you can receive support and provide feedback. In addition, the following rules apply for an instance of DataRow. The default value is DbNull. Value for all except the strongly typed null columns where it is the appropriate strongly typed null value. All non-null values, including defaults, are always written out while serializing to XML.
The opposite is true for a DataTable : a null value is implicit and the default value is explicit. Rows created using NewRow or similar methods are assigned the DataColumn's default value. The IsNull method returns true for both DbNull. Value and INullable. When comparing null values, it is important to understand the difference between the way the Equals method evaluates null values in System.
SqlTypes as compared with the way it works with CLR types. All of the System. SqlTypes Equals methods use database semantics for evaluating null values: if either or both of the values is null, the comparison yields null. SqlTypes will yield true if both are null. This reflects the difference between using an instance method such as the CLR String. The following example demonstrates the difference in results between the SqlString. Equals method and the String.
Equals method when each is passed a pair of null values and then a pair of empty strings. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Is this page helpful? You would have to return a Nullable OF Integer in order to communicate the abscence of a value. However, VB doesn't have a null value.
Instead it uses Nothing. Nothing represents the empty value for both value and reference types. It is convertible to any value type and simply represents the equivalent of default T in C. Many people say null when talking about VB but really mean Nothing.
If this is the case then yes, you can return Nothing from an Integer returning function. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Vb Function returning null Ask Question. Asked 12 years, 9 months ago. Active 7 years, 7 months ago. Viewed 29k times.
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