Explicit Data Type Conversion in Visual Basic

Explicit Data Type Conversion in Visual Basic

Data Types

An explicit conversion uses a type conversion keyword. Visual Basic provides several such keywords. These keywords work like functions, but the compiler generates the code inline, so execution is slightly faster than with a function call.

CType Function

The CType Function operates on two arguments. The first is the expression to be converted, and the second is the destination data type or object. Note that the first argument must be an expression, not a type. CType is an inline function, meaning the compiled code makes the conversion, often without generating a function call. This improves performance.

Code example

Dim objVal As Object
Dim oRange As Excel.Range

'Perform conversion
oRange = CType(objVal,Excel.Range)

List of inbuilt conversion functions

Conversion Keywords Data type Expression to be converted
CBool Boolean Any numeric type (including Byte, SByte, and enumerated types), String, Object
CByte Byte Any numeric type (including SByte and enumerated types), Boolean, String, Object
CChar Char String, Object
CDate Date String, Object
CDbl Double Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CDec Decimal Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CInt Integer Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CLng Long Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CObj Object Any type
CSByte SByte Any numeric type (including Byte and enumerated types), Boolean, String, Object
CShort Short Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CSng Single Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CStr String Any numeric type (including Byte, SByte, and enumerated types), Boolean, Char, Char array, Date, Object
Type Type specified following by comman (,) When converting to an elementary data type (including an array of an elementary type), the same types as allowed for the corresponding conversion keyword When converting to a composite data type, the interfaces it implements and the classes from which it inherits When converting to a class or structure on which you have overloaded CType, that class or structure
CUInt UInteger Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CULng ULong Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object
CUShort UShort Any numeric type (including Byte, SByte, and enumerated types), Boolean, String, Object

Note: Specifying CType to convert from one class type to another fails at run time if the source type does not derive from the destination type. Such a failure throws an InvalidCastException exception.

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