Single.Equals Method (Object)

Returns a value indicating whether this instance is equal to a specified object.

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

public override bool Equals(
	Object obj
)

Parameters

obj
Type: System.Object
An object to compare with this instance.

Return Value

Type: System.Boolean
true if obj is an instance of Single and equals the value of this instance; otherwise, false.

The Equals method should be used with caution, because two apparently equivalent values can be unequal due to the differing precision of the two values. The following example reports that the Single value .3333 and the Single returned by dividing 1 by 3 are unequal.


// Initialize two floats with apparently identical values
float float1 = .33333f;
object float2 = 1/3;
// Compare them for equality
Console.WriteLine(float1.Equals(float2));    // displays false


Rather than comparing for equality, one recommended technique involves defining an acceptable margin of difference between two values (such as .01% of one of the values). If the absolute value of the difference between the two values is less than or equal to that margin, the difference is likely to be due to differences in precision and, therefore, the values are likely to be equal. The following example uses this technique to compare .33333 and 1/3, the two Single values that the previous code example found to be unequal.


// Initialize two floats with apparently identical values
float float1 = .33333f;
object float2 = (float) 1/3;
// Define the tolerance for variation in their values
float difference = Math.Abs(float1 * .0001f);

// Compare the values
// The output to the console indicates that the two values are equal
if (Math.Abs(float1 - (float) float2) <= difference)
   Console.WriteLine("float1 and float2 are equal.");
else
   Console.WriteLine("float1 and float2 are unequal.");


In this case, the values are equal.

NoteNote

Because Epsilon defines the minimum expression of a positive value whose range is near zero, the margin of difference must be greater than Epsilon. Typically, it is many times greater than Epsilon.

The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. Consequently, a comparison of two particular numbers might change between versions of the .NET Framework because the precision of the numbers' internal representation might change.

The following code example demonstrates the Equals method.


obj1 = (Single)500;
if (a.Equals(obj1)) {
    Console.WriteLine("The value type and reference type values are equal.");
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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