A member variable (declared at module level, outside any procedure) typically has the same lifetime as the element in which it is declared. A nonshared variable declared in a class or structure exists as a separate copy for each instance of the class or structure in which it is declared. Each such variable has the same lifetime as its instance. However, a Shared variable has only a single lifetime, which lasts for the entire time your application is running.

A local variable (declared inside a procedure) exists only while the procedure in which it is declared is running. This applies also to that procedure's parameters and to any function return. However, if that procedure calls other procedures, the local variables retain their values while the called procedures are running.

A local variable's lifetime begins when control enters the procedure in which it is declared. Every local variable is initialized to the default value for its data type as soon as the procedure begins running. When the procedure encounters a Dim statement that specifies initial values, it sets those variables to those values, even if your code had already assigned other values to them.

Each member of a structure variable is initialized as if it were a separate variable. Similarly, each element of an array variable is initialized individually.

Variables declared within a block inside a procedure (such as a For loop) are initialized on entry to the procedure. These initializations take effect whether or not your code ever executes the block.

When a procedure terminates, the values of its local variables are not preserved, and Visual Basic reclaims their memory. The next time you call the procedure, all its local variables are created afresh and reinitialized.

When an instance of a class or structure terminates, its nonshared variables lose their memory and their values. Each new instance of the class or structure creates and reinitializes its nonshared variables. However, Shared variables are preserved until your application stops running.

If you declare a local variable with the Static keyword, its lifetime is longer than the execution time of its procedure. The following table shows how the procedure declaration determines how long a Static variable exists.

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