If myString Is Nothing Or myString = "" Then
Lset vba 6.0 code#
Therefore, you can combine the two single statements shown in the preceding statements into the following shorter, single statement: Dim aString As String = "Susan Kallenbach" Handling Empty and Blank Stringsįor decades, Visual Basic developers have become accustomed to using the code pattern shown in the following to check whether a string variable is not defined ( Nothing) or points to an empty string: Dim myString As String Just as with other base data types, declaration and assignment can both take place in an assignment. Strings are defined as a list of characters between quotes, as shown in the following example: aString = "Susan Kallenbach" The instance of the String object is created at IML level. You can then immediately use the new string variable. For example, you can declare a string with the statement: Dim aString As String Declaring and Defining StringsĪs with all other base data types, you can declare strings without using the New keyword you can perform assignments directly in the program. The following sections demonstrate the handling of strings with the help of a few short examples.
But they are not only superfluous-you can reach the same goal much more elegantly with the existing methods and properties of the String object-but they also slow down programs unnecessarily, because internally they call the String object functions anyhow.įor (almost) all the old string functions, there is a corresponding class function that you should use as a substitute. This was the result of the new implementation of the data type String, which is created by instantiating a class, like other objects.Īlmost all commands and functions that were “standalone” in Visual Basic 6.0 and VBA still exist in the. NET Framework 1.0, Microsoft introduced a completely new way to approach string programming in Visual Basic. Strings-Yesterday and Todayīeginning with Visual Studio 2002 and. At the end of this section, you’ll find an example application that illustrates the most important string manipulation functions. The following sections provide an overview of the special characteristic of strings in the BCL.
You can read more about reference types in “Chapter 12, Typecasting and Boxing Value Types.” For strings, however, when assigning an instance to an object variable, the content is cloned, which also deviates from the default. The equal operator would also need to assign just one reference. Strictly speaking, since strings are reference types, they need to be instantiated with New. Similar to nullables (see Chapter 18) when boxing, CLR interrupts the default behavior for reference types and changes it.
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