Double Structure

July 28, 2014

Represents a double-precision floating-point number.

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

public struct Double : IComparable, IComparable<double>, 
	IConvertible, IEquatable<double>, IFormattable

The Double type exposes the following members.

  NameDescription
Public methodCompareTo(Double)Compares this instance to a specified double-precision floating-point number and returns an integer that indicates whether the value of this instance is less than, equal to, or greater than the value of the specified double-precision floating-point number.
Public methodCompareTo(Object)Compares this instance to a specified object and returns an integer that indicates whether the value of this instance is less than, equal to, or greater than the value of the specified object.
Public methodEquals(Double)Returns a value indicating whether this instance and a specified Double object represent the same value.
Public methodEquals(Object)Returns a value indicating whether this instance is equal to a specified object. (Overrides ValueType.Equals(Object).)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Overrides ValueType.GetHashCode().)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodGetTypeCodeReturns the TypeCode for value type Double.
Public methodStatic memberIsInfinityReturns a value indicating whether the specified number evaluates to negative or positive infinity
Public methodStatic memberIsNaNReturns a value indicating whether the specified number evaluates to a value that is not a number (NaN).
Public methodStatic memberIsNegativeInfinityReturns a value indicating whether the specified number evaluates to negative infinity.
Public methodStatic memberIsPositiveInfinityReturns a value indicating whether the specified number evaluates to positive infinity.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodStatic memberParse(String)Converts the string representation of a number to its double-precision floating-point number equivalent.
Public methodStatic memberParse(String, NumberStyles)Converts the string representation of a number in a specified style to its double-precision floating-point number equivalent.
Public methodStatic memberParse(String, IFormatProvider)Converts the string representation of a number in a specified culture-specific format to its double-precision floating-point number equivalent.
Public methodStatic memberParse(String, NumberStyles, IFormatProvider)Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent.
Public methodToString()Converts the numeric value of this instance to its equivalent string representation. (Overrides ValueType.ToString().)
Public methodToString(IFormatProvider)Converts the numeric value of this instance to its equivalent string representation using the specified culture-specific format information.
Public methodToString(String)Converts the numeric value of this instance to its equivalent string representation, using the specified format.
Public methodToString(String, IFormatProvider)Converts the numeric value of this instance to its equivalent string representation using the specified format and culture-specific format information.
Public methodStatic memberTryParse(String, Double)Converts the string representation of a number to its double-precision floating-point number equivalent. A return value indicates whether the conversion succeeded or failed.
Public methodStatic memberTryParse(String, NumberStyles, IFormatProvider, Double)Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent. A return value indicates whether the conversion succeeded or failed.
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  NameDescription
Public operatorStatic memberEqualityReturns a value that indicates whether two specified Double values are equal.
Public operatorStatic memberGreaterThanReturns a value that indicates whether a specified Double value is greater than another specified Double value.
Public operatorStatic memberGreaterThanOrEqualReturns a value that indicates whether a specified Double value is greater than or equal to another specified Double value.
Public operatorStatic memberInequalityReturns a value that indicates whether two specified Double values are not equal.
Public operatorStatic memberLessThanReturns a value that indicates whether a specified Double value is less than another specified Double value.
Public operatorStatic memberLessThanOrEqualReturns a value that indicates whether a specified Double value is less than or equal to another specified Double value.
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  NameDescription
Public fieldStatic memberEpsilonRepresents the smallest positive Double value greater than zero. This field is constant.
Public fieldStatic memberMaxValueRepresents the largest possible value of a Double. This field is constant.
Public fieldStatic memberMinValueRepresents the smallest possible value of a Double. This field is constant.
Public fieldStatic memberNaNRepresents a value that is not a number (NaN). This field is constant.
Public fieldStatic memberNegativeInfinityRepresents negative infinity. This field is constant.
Public fieldStatic memberPositiveInfinityRepresents positive infinity. This field is constant.
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  NameDescription
Explicit interface implemetationPrivate methodIConvertible.ToBooleanInfrastructure. For a description of this member, see IConvertible.ToBoolean.
Explicit interface implemetationPrivate methodIConvertible.ToByteInfrastructure. For a description of this member, see IConvertible.ToByte.
Explicit interface implemetationPrivate methodIConvertible.ToCharInfrastructure. This conversion is not supported. Attempting to use this method throws an InvalidCastException.
Explicit interface implemetationPrivate methodIConvertible.ToDateTimeInfrastructure. This conversion is not supported. Attempting to use this method throws an InvalidCastException
Explicit interface implemetationPrivate methodIConvertible.ToDecimalInfrastructure. For a description of this member, see IConvertible.ToDecimal.
Explicit interface implemetationPrivate methodIConvertible.ToDoubleInfrastructure. For a description of this member, see IConvertible.ToDouble.
Explicit interface implemetationPrivate methodIConvertible.ToInt16Infrastructure. For a description of this member, see IConvertible.ToInt16.
Explicit interface implemetationPrivate methodIConvertible.ToInt32Infrastructure. For a description of this member, see IConvertible.ToInt32.
Explicit interface implemetationPrivate methodIConvertible.ToInt64Infrastructure. For a description of this member, see IConvertible.ToInt64.
Explicit interface implemetationPrivate methodIConvertible.ToSByteInfrastructure. For a description of this member, see IConvertible.ToSByte.
Explicit interface implemetationPrivate methodIConvertible.ToSingleInfrastructure. For a description of this member, see IConvertible.ToSingle.
Explicit interface implemetationPrivate methodIConvertible.ToTypeInfrastructure. For a description of this member, see IConvertible.ToType.
Explicit interface implemetationPrivate methodIConvertible.ToUInt16Infrastructure. For a description of this member, see IConvertible.ToUInt16.
Explicit interface implemetationPrivate methodIConvertible.ToUInt32Infrastructure. For a description of this member, see IConvertible.ToUInt32.
Explicit interface implemetationPrivate methodIConvertible.ToUInt64Infrastructure. For a description of this member, see IConvertible.ToUInt64.
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The Double value type represents a double-precision 64-bit number with values ranging from negative 1.79769313486232e308 to positive 1.79769313486232e308, as well as positive or negative zero, PositiveInfinity, NegativeInfinity, and Not-a-Number (NaN).

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

Double 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 Double, then the other operand is required to be an integral type or a floating-point type (Double or Single). Prior to performing the operation, if the other operand is not a Double, it is converted to Double, and the operation is performed using at least Double range and precision. If the operation produces a numeric result, the type of the result is Double.

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 Double value contains 15 decimal digits of precision, although a maximum of 17 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.

In addition, the result of arithmetic and assignment operations with Double values may differ slightly by platform because of the loss of precision of the Double type.

Interface Implementations

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

Double Values and XAML Parsing

When a Double value is processed as a XAML attribute value, it does not preserve the full precision that is implied by the definition of Double in code and in the runtime. This is because native code is used as part of the XAML parser operations, and numeric values that are applicable to a user interface are deliberately optimized.

XAML also includes several properties that have an underlying property type of Double, but where the expected values fall between 0 and 1.0. This is typically noted in the reference documentation for that property, and often noted in the XAML syntax. An example of such a property is UIElement.Opacity.

The following example illustrates the use of Double:


// Temperature class stores the value as Double
// and delegates most of the functionality 
// to the Double implementation.
public class Temperature : IComparable, IFormattable
{
   // IComparable.CompareTo implementation.
   public int CompareTo(object obj)
   {
      if (obj == null) return 1;

      Temperature temp = obj as Temperature;
      if (temp != null) 
         return m_value.CompareTo(temp.m_value);
      else
         throw new ArgumentException("object is not a Temperature");
   }

   // IFormattable.ToString implementation.
   public string ToString(string format, IFormatProvider provider)
   {
      if (format != null)
      {
         if (format.Equals("F"))
         {
            return String.Format("{0}'F", this.Value.ToString());
         }
         if (format.Equals("C"))
         {
            return String.Format("{0}'C", this.Celsius.ToString());
         }
      }

      return m_value.ToString(format, provider);
   }

   // Parses the temperature from a string in form
   // [ws][sign]digits['F|'C][ws]
   public static Temperature Parse(string s, NumberStyles styles, IFormatProvider provider)
   {
      Temperature temp = new Temperature();

      if (s.TrimEnd(null).EndsWith("'F"))
      {
         temp.Value = Double.Parse(s.Remove(s.LastIndexOf('\''), 2), styles, provider);
      }
      else if (s.TrimEnd(null).EndsWith("'C"))
      {
         temp.Celsius = Double.Parse(s.Remove(s.LastIndexOf('\''), 2), styles, provider);
      }
      else
      {
         temp.Value = Double.Parse(s, styles, provider);
      }

      return temp;
   }

   // The value holder
   protected double m_value;

   public double Value
   {
      get
      {
         return m_value;
      }
      set
      {
         m_value = value;
      }
   }

   public double Celsius
   {
      get
      {
         return (m_value - 32.0) / 1.8;
      }
      set
      {
         m_value = 1.8 * value + 32.0;
      }
   }
}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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.

Caution noteCaution:

Assigning an instance of this type is not thread safe on all hardware platforms because the binary representation of that instance might be too large to assign in a single atomic operation.

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