Conversion is the process of changing a value from one type to another. Conversions may either be widening or narrowing. A widening conversion is a conversion from one type to another type that is guaranteed to be able to contain it. Widening conversions never fail. A narrowing conversion may fall into one of two categories. One category is a conversion from one type to another type that is not guaranteed to be able to contain it. The other category is a conversion between types that are sufficiently unrelated as to have no obvious conversion. Narrowing conversions, which entail loss of information, may fail.
8.1 Implicit and Explicit Conversions | 8.5 Array Covariance | 8.8 Widening Conversions | 8.9 Narrowing Conversions | Conversion Summary (Visual Basic Language Reference) | Type Conversions (Visual Basic Language Concepts)