Artigo
11/18/2011

Single Structure

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Represents a single-precision floating-point number.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Structure Single _
    Implements IComparable, IFormattable, IConvertible, IComparable(Of Single),  _
    IEquatable(Of Single)

[ComVisibleAttribute(true)]
public struct Single : IComparable, IFormattable, 
    IConvertible, IComparable<float>, IEquatable<float>

The Single type exposes the following members.

Methods

	Name	Description
	CompareTo(Object)	Compares this instance to a specified object and returns an integer that indicates whether the value of this instance is greater than, less than, or equal to the value of the specified object.
	CompareTo(Single)	Compares this instance to a specified single-precision floating-point number and returns an integer that indicates whether the value of this instance is greater than, less than, or equal to the value of the specified single-precision floating-point number.
	Equals(Object)	Returns a value indicating whether this instance is equal to a specified object. (Overrides ValueType.Equals(Object).)
	Equals(Single)	Returns a value indicating whether this instance and a specified Single object represent the same value.
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Returns the hash code for this instance. (Overrides ValueType.GetHashCode().)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	GetTypeCode	Returns the TypeCode for value type Single.
	IsInfinity	Returns a value indicating whether the specified number evaluates to negative or positive infinity.
	IsNaN	Returns a value indicating whether the specified number evaluates to not a number (NaN).
	IsNegativeInfinity	Returns a value indicating whether the specified number evaluates to negative infinity.
	IsPositiveInfinity	Returns a value indicating whether the specified number evaluates to positive infinity.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Parse(String)	Converts the string representation of a number to its single-precision floating-point number equivalent.
	Parse(String, NumberStyles)	Converts the string representation of a number in a specified style to its single-precision floating-point number equivalent.
	Parse(String, IFormatProvider)	Converts the string representation of a number in a specified culture-specific format to its single-precision floating-point number equivalent.
	Parse(String, NumberStyles, IFormatProvider)	Converts the string representation of a number in a specified style and culture-specific format to its single-precision floating-point number equivalent.
	ToString()	Converts the numeric value of this instance to its equivalent string representation. (Overrides ValueType.ToString().)
	ToString(IFormatProvider)	Converts the numeric value of this instance to its equivalent string representation using the specified culture-specific format information.
	ToString(String)	Converts the numeric value of this instance to its equivalent string representation, using the specified format.
	ToString(String, IFormatProvider)	Converts the numeric value of this instance to its equivalent string representation using the specified format and culture-specific format information.
	TryParse(String, Single%)	Converts the string representation of a number to its single-precision floating-point number equivalent. A return code indicates whether the conversion succeeded or failed.
	TryParse(String, NumberStyles, IFormatProvider, Single%)	Converts the string representation of a number in a specified style and culture-specific format to its single-precision floating-point number equivalent. A return code indicates whether the conversion succeeded or failed.

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Fields

	Name	Description
	Epsilon	Represents the smallest positive Single value greater than zero. This field is constant.
	MaxValue	Represents the largest possible value of Single. This field is constant.
	MinValue	Represents the smallest possible value of Single. This field is constant.
	NaN	Represents not a number (NaN). This field is constant.
	NegativeInfinity	Represents negative infinity. This field is constant.
	PositiveInfinity	Represents positive infinity. This field is constant.

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Explicit Interface Implementations

	Name	Description
	IConvertible.ToBoolean	Infrastructure. For a description of this member, see IConvertible.ToBoolean.
	IConvertible.ToByte	Infrastructure. For a description of this member, see IConvertible.ToByte.
	IConvertible.ToChar	Infrastructure. This conversion is not supported. Attempting to use this method throws an InvalidCastException.
	IConvertible.ToDateTime	Infrastructure. This conversion is not supported. Attempting to use this method throws an InvalidCastException.
	IConvertible.ToDecimal	Infrastructure. For a description of this member, see IConvertible.ToDecimal.
	IConvertible.ToDouble	Infrastructure. For a description of this member, see IConvertible.ToDouble.
	IConvertible.ToInt16	Infrastructure. For a description of this member, see IConvertible.ToInt16.
	IConvertible.ToInt32	Infrastructure. For a description of this member, see IConvertible.ToInt32.
	IConvertible.ToInt64	Infrastructure. For a description of this member, see IConvertible.ToInt64.
	IConvertible.ToSByte	Infrastructure. For a description of this member, see IConvertible.ToSByte.
	IConvertible.ToSingle	Infrastructure. For a description of this member, see IConvertible.ToSingle.
	IConvertible.ToType	Infrastructure. For a description of this member, see IConvertible.ToType.
	IConvertible.ToUInt16	Infrastructure. For a description of this member, see IConvertible.ToUInt16.
	IConvertible.ToUInt32	Infrastructure. For a description of this member, see IConvertible.ToUInt32.
	IConvertible.ToUInt64	Infrastructure. For a description of this member, see IConvertible.ToUInt64.

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Remarks

The Single value type represents a single-precision 32-bit number with values ranging from negative 3.402823e38 to positive 3.402823e38, as well as positive or negative zero, PositiveInfinity, NegativeInfinity, and not a number (NaN).

Single complies with the IEC 60559:1989 (IEEE 754) standard for binary floating-point arithmetic.

Single provides methods to compare instances of this type, convert the value of an instance to its string representation, and convert the string representation of a number to an instance of this type. For information about how format specification codes control the string representation of value types, see Formatting Types, Standard Numeric Format Strings, and Custom Numeric Format Strings.

Using Floating-Point Numbers

When performing binary operations, if one of the operands is a floating-point type, Single or Double, then the other operand is required to be an integral type or a floating-point type. The operation is evaluated as follows:

If one of the operands is of an integral type, then that operand is converted to the floating-point type of the other operand.
Then, if either of the operands is Double, the other operand is converted to Double, and the operation is performed using at least the range and precision of the Double. For numeric operations, the type of the result is Double.
Otherwise, the operation is performed using at least the range and precision of the Single type and, for numeric operations, the type of the result is Single.

The floating-point operators, including the assignment operators, do not throw exceptions. Instead, in exceptional situations the result of a floating-point operation is zero, infinity, or NaN, as described below:

If the result of a floating-point operation is too small for the destination format, the result of the operation is zero.
If the magnitude of the result of a floating-point operation is too large for the destination format, the result of the operation is PositiveInfinity or NegativeInfinity, as appropriate for the sign of the result.
If a floating-point operation is invalid, the result of the operation is NaN.
If one or both operands of a floating-point operation are NaN, the result of the operation is NaN.

Floating-Point Values and Loss of Precision

Remember that a floating-point number can only approximate a decimal number, and that the precision of a floating-point number determines how accurately that number approximates a decimal number. By default, a Single value contains only 7 decimal digits of precision, although a maximum of 9 digits is maintained internally. The precision of a floating-point number has several consequences:

Two floating-point numbers that appear equal for a particular precision might not compare equal because their least significant digits are different.
A mathematical or comparison operation that uses a floating-point number might not yield the same result if a decimal number is used because the floating-point number might not exactly approximate the decimal number.
A value might not roundtrip if a floating-point number is involved. A value is said to roundtrip if an operation converts an original floating-point number to another form, an inverse operation transforms the converted form back to a floating-point number, and the final floating-point number is equal to the original floating-point number. The roundtrip might fail because one or more least significant digits are lost or changed in a conversion.

Interface Implementations

This type implements the interfaces IComparable, IComparable<T>, IFormattable, IConvertible, and IEquatable<T>. Use the Convert class for conversions instead of this type's explicit interface member implementation of IConvertible.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

All members of this type are thread safe. Members that appear to modify instance state actually return a new instance initialized with the new value. As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.

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