Type Conversion Tables
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Widening conversion occurs when a value of one type is converted to another type that is of equal or greater size. For example, the conversion of a Byte to an Int16 value is a widening conversion because all possible Byte values lie within the range of Int16.MinValue to Int16.MaxValue. A narrowing conversion occurs when a value of one type is converted to a value of another type that is of a smaller size. For example, the conversion of an Int64 to an Int32 value is a narrowing conversion because some possible Int64 values lie outside the range of Int32.MinValue to Int32.MaxValue. The tables in this topic illustrate the behaviors exhibited by both types of conversions.
Widening Conversions
The following table describes the widening conversions that can be performed without the loss of information.
Type |
Can be converted without data loss to |
|---|---|
Byte |
UInt16, Int16, UInt32, Int32, UInt64, Int64, Single, Double, Decimal |
SByte |
Int16, Int32, Int64, Single, Double, Decimal |
Int16 |
Int32, Int64, Single, Double, Decimal |
UInt16 |
UInt32, Int32, UInt64, Int64, Single, Double, Decimal |
Char |
UInt16, UInt32, Int32, UInt64, Int64, Single, Double, Decimal |
Int32 |
Int64, Double, Decimal |
UInt32 |
Int64, Double, Decimal |
Int64 |
Decimal |
UInt64 |
Decimal |
Single |
Double |
Some widening conversions to Single or Double can cause a loss of precision. The following table describes the widening conversions that sometimes result in a loss of information.
Type |
Can be converted to |
|---|---|
Int32 |
Single |
UInt32 |
Single |
Int64 |
Single, Double |
UInt64 |
Single, Double |
Decimal |
Single, Double |
Narrowing Conversions
A narrowing conversion to Single or Double can cause a loss of information. If the target type cannot properly express the magnitude of the source, then the resulting type is set to the constant PositiveInfinity or NegativeInfinity. The value of PositiveInfinity is the result of dividing a positive number by zero and is returned when the value of a Single or Double exceeds the value of the MaxValue field. The value of NegativeInfinity is the result of dividing a negative number by zero and is returned when the value of a Single or Double falls below the value of the MinValue field. A conversion from a Double to a Single might result in PositiveInfinity or NegativeInfinity.
A narrowing conversion can also result in a loss of information for other data types. However, if the value of a type being converted falls outside of the range specified by the target type's MaxValue and MinValue fields, and the conversion is checked by the runtime to ensure that the value of the target type does not exceed its MaxValue or MinValue, then an OverflowException is thrown. Conversions performed with the System.Convert class are always checked in this manner.
The following table lists conversions that throw an OverflowException using System.Convert or any checked conversion if the value of the type being converted is outside the defined range of the target type.
Type |
Can be converted to |
|---|---|
Byte |
Sbyte |
SByte |
Byte, UInt16, UInt32, UInt64 |
Int16 |
Byte, SByte, UInt16 |
UInt16 |
Byte, SByte, Int16 |
Int32 |
Byte, SByte, Int16, UInt16, UInt32 |
UInt32 |
Byte, SByte, Int16, UInt16, Int32 |
Int64 |
Byte, SByte, Int16, UInt16, Int32, UInt32, UInt64 |
UInt64 |
Byte, SByte, Int16, UInt16, Int32, UInt32, Int64 |
Decimal |
Byte, SByte, Int16, UInt16, Int32, UInt32, Int64, UInt64 |
Single |
Byte, SByte, Int16, UInt16, Int32, UInt32, Int64, UInt64 |
Double |
Byte, SByte, Int16, UInt16, Int32, UInt32, Int64, UInt64 |