Comparison Operators (Visual Basic)

The following are the comparison operators defined in Visual Basic.

< operator

<= operator

> operator

>= operator

= operator

<> operator

Is Operator (Visual Basic)

IsNot Operator (Visual Basic)

Like Operator (Visual Basic)

These operators compare two expressions to determine whether or not they are equal, and if not, how they differ. Is, IsNot, and Like are discussed in detail on separate Help pages. The relational comparison operators are discussed in detail on this page.

result = expression1 comparisonoperator expression2 
result = object1 [Is | IsNot] object2 
result = string Like pattern

Parts

• result
  Required. A Boolean value representing the result of the comparison.

• expression
  Required. Any expression.

• comparisonoperator
  Required. Any relational comparison operator.

• object1, object2
  Required. Any reference object names.

• string
  Required. Any String expression.

• pattern
  Required. Any String expression or range of characters.

Remarks

The following table contains a list of the relational comparison operators and the conditions that determine whether result is True or False.

The Is operator, the IsNot operator, and the Like operator have specific comparison functionalities that differ from the operators in the preceding table.

Comparing Numbers

When you compare an expression of type Single to one of type Double, the Single expression is converted to Double. This behavior is opposite to the behavior found in Visual Basic 6.

Similarly, when you compare an expression of type Decimal to an expression of type Single or Double, the Decimal expression is converted to Single or Double. For Decimal expressions, any fractional value less than 1E-28 might be lost. Such fractional value loss may cause two values to compare as equal when they are not. For this reason, you should take care when using equality (=) to compare two floating-point variables. It is safer to test whether the absolute value of the difference between the two numbers is less than a small acceptable tolerance.

Floating-point Imprecision

When you work with floating-point numbers, keep in mind that they do not always have a precise representation in memory. This could lead to unexpected results from certain operations, such as value comparison and the Mod Operator (Visual Basic). For more information, see Troubleshooting Data Types (Visual Basic).

Comparing Strings

When you compare strings, the string expressions are evaluated based on their alphabetical sort order, which depends on the Option Compare setting.

Option Compare Binary bases string comparisons on a sort order derived from the internal binary representations of the characters. The sort order is determined by the code page. The following example shows a typical binary sort order.

A < B < E < Z < a < b < e < z < À < Ê < Ø < à < ê < ø

Option Compare Text bases string comparisons on a case-insensitive, textual sort order determined by your application's locale. When you set Option Compare Text and sort the characters in the preceding example, the following text sort order applies:

(A=a) < (À= à) < (B=b) < (E=e) < (Ê= ê) < (Ø = ø) < (Z=z)

Locale Dependence

When you set Option Compare Text, the result of a string comparison can depend on the locale in which the application is running. Two characters might compare as equal in one locale but not in another. If you are using a string comparison to make important decisions, such as whether to accept an attempt to log on, you should be alert to locale sensitivity. Consider either setting Option Compare Binary or calling the StrComp, which takes the locale into account.

Typeless Programming with Relational Comparison Operators

The use of relational comparison operators with Object expressions is not allowed under Option Strict On. When Option Strict is Off, and either expression1 or expression2 is an Object expression, the run-time types determine how they are compared. The following table shows how the expressions are compared and the result from the comparison, depending on the runtime type of the operands.

Numeric comparisons treat Nothing as 0. String comparisons treat Nothing as "" (an empty string).

Overloading

The relational comparison operators (<. <=, >, >=, =, <>) can be overloaded, which means that a class or structure can redefine their behavior when an operand has the type of that class or structure. If your code uses any of these operators on such a class or structure, be sure you understand the redefined behavior. For more information, see Operator Procedures (Visual Basic).

Notice that the = Operator (Visual Basic) can be overloaded only as a relational comparison operator, not as an assignment operator.

Example

The following example shows various uses of relational comparison operators, which you use to compare expressions. Relational comparison operators return a Boolean result that represents whether or not the stated expression evaluates to True. When you apply the > and < operators to strings, the comparison is made using the normal alphabetical sorting order of the strings. This order can be dependent on your locale setting. Whether the sort is case-sensitive or not depends on the Option Compare setting.

Dim testResult As Boolean
testResult = 45 < 35
testResult = 45 = 45
testResult = 4 <> 3
testResult = "5" > "4444"

In the preceding example, the first comparison returns False and the remaining comparisons return True.

See Also

Tasks

Troubleshooting Data Types (Visual Basic)

Reference

= Operator (Visual Basic)

Operator Precedence in Visual Basic

Operators Listed by Functionality (Visual Basic)

InvalidCastException

Concepts

Comparison Operators in Visual Basic