The Ultimate VB .NET and ASP.NET Code Book
IV: VB.NET Data Types
The following table lists the data types that are available in VB.NET, listed alongside their Common Language Runtime (CLR) base type.
| VB DATA TYPE NAME | CAN HOLD | SIZE IN MEMORY | CORRESPONDING CLR TYPE |
|---|---|---|---|
| Boolean | True or False | 2 bytes | System.Boolean |
| Byte | 0 to 255 | 1 byte | System.Byte |
| Char | One single character | 2 bytes | System.Char |
| Date | January 1, 0001 00:00:00 through to December 31, 9999 11:59:59 PM | 8 bytes | System.DateTime |
| Decimal | 0 through to +/- 79,228,162,514,264,337, 593,543,950,335 with no decimal point; 0 through +/-7.9228162514264337593543950335 (with 28 places to the right of the decimal point) | 16 bytes | System.Decimal |
| Double (double-precision floating-point) | -1.79769313486231570E+308 through to -4.94065645841246544E-324 fornegative values; 4.94065645841246544E-324 through to 1.79769313486231570E+308 for positive values | 8 bytes | System.Double |
| Integer | -2,147,483,648 through to 2,147,483,647 | 4 bytes | System.Int32 |
| Long (long integer) | 9,223,372,036,854,775,807 -9,223,372,036,854,775,808 through to | 8 bytes | System.Int64 |
| Object | Any type can be stored in an Object variable | 4 bytes | System.Object (class) |
| Short | -32,768 through to 32,767 | 2 bytes | System.Int16 |
| Single (single-precision floating-point) | -3.4028235E+38 through to -1.401298E-45for negative values; 1.401298E-45 through 3.4028235E+38 for positive values | 4 bytes | System.Single |
| String | 0 to approximately 2 billion Unicode characters | Depends on platform | System.String (class) |
| User-Defined Types | Each member of the structure is determined by its data type | Depends on platform | System.ValueType (inherits from) |
In the .NET world, you officially have two different types : value types and reference types. Value types simply contain core values and are stored on the application stack. Sample value types include Boolean, Integer, and Date.
Reference types are stored on the runtime heap, pointing to a particular object in memory. All objects derived from classes are reference types, including the String type, all arrays, forms, and so on.
In the many applications, this behind-the-scenes difference will have no or little impact on our programming. With powerful, highly requested applications, however, take the following two details into account:
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All reference types are handled by the .NET Framework garbage collection process. This means that unused objects are marked for deletion and destroyed, say, every few minutes. At busy times, this can result in a lot of objects just consuming memory, waiting to be destroyed . So, where possible, use the more efficient value types.
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Strings are more efficiently concatenated using the StringBuilder class. Using the simple & concatenation command can result in wasted memory strings that require garbage collection.