Variants

In This Topic

Variant Operators
Explicit Type Change
See Also

Variants are value-type pairs, which facilitate the type conversion of values, as well as mathematical and logical operations with values of different type. Variants are represented by the NVariant class.

Each variant has a value, which can be obtained from its Value property. The variant value is an object from the type, which can be obtained from the Type property. The currently supported types of variant values are enumerated the VariantType enumeration.

Variant Operators

The power of variants is their ability to provide transparent handling of type conversion so that you can perform common mathematical and logical operations, without caring for the actual type of the involved values. The NVariant class defines the following set of operators, which you can use:

Type Cast Operators - you can cast a variant to a value of specific type. For example:

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// create a float variant NVariant v1 = new NVariant(1.5f); // cast to double value double d = (double)v1;

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' create a float variant Dim v1 As New NVariant(1.5F) ' convert to double value Dim d As Double = Convert.ToDouble(v1)

Unary Arithmetic Operators - you can use unary + and - operators. For example:

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// create a float variant NVariant v1 = new NVariant(1.5f); // use unary minus - res is a float variant with value -1.5f NVariant res = -v1;

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' create a float variant Dim v1 As New NVariant(1.5F) ' use unary minus - res is a float variant with value -1.5f Dim res As NVariant res = NVariant.op_UnaryNegation(v1)

Binary Arithmetic Operators - you can use +, -, *, / and ^ operators. For example:

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// create a float variant NVariant v1 = new NVariant(1.5f); // create an int variant NVariant v2 = new NVariant(3); // use binary plus - res is a float variant with value 4.5f NVariant res = v1 + v2;

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' create a float variant Dim v1 As New NVariant(1.5F) ' create an int variant Dim v2 As New NVariant(3) ' use binary plus - res is a float variant with value 4.5f Dim res As NVariant = NVariant.op_Addition(v1, v2)

Visual Basic

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' create a float variant
Dim v1 As New NVariant(1.5F)
' create an int variant
Dim v2 As New NVariant(3)
' use binary plus - res is a float variant with value 4.5f
Dim res As NVariant = NVariant.op_Addition(v1, v2)

Binary Comparison Operators - you can use >, <, >=, <=, == and != operators. For example:

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// create a float variant NVariant v1 = new NVariant(1.5f); // create an int variant NVariant v2 = new NVariant(3); // use less operator - res is a boolean variant with value true NVariant res = (v1 < v2);

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// create a float variant
NVariant v1 = new NVariant(1.5f);
// create an int variant
NVariant v2 = new NVariant(3);
// use less operator - res is a boolean variant with value true
NVariant res = (v1 < v2);

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' create a float variant Dim v1 As New NVariant(1.5F) ' create an int variant Dim v2 As New NVariant(3) ' use less operator - res is a boolean variant with value true Dim res As NVariant = NVariant.op_LessThan(v1, v2)

Visual Basic

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' create a float variant
Dim v1 As New NVariant(1.5F)
' create an int variant
Dim v2 As New NVariant(3)
' use less operator - res is a boolean variant with value true
Dim res As NVariant = NVariant.op_LessThan(v1, v2)

Binary String Operators - you can use & in your code, which uses variants. For example:

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// create a float variant NVariant v1 = new NVariant(1.5f); // create a string variant NVariant v2 = new NVariant("Value is: "); // use & operator - res is a string variant with value "Value is: 1.5" NVariant res = v2 & v1;

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// create a float variant 
NVariant v1 = new NVariant(1.5f);
// create a string variant 
NVariant v2 = new NVariant("Value is: ");
// use & operator - res is a string variant with value "Value is: 1.5" 
NVariant res = v2 & v1;

Visual Basic	Copy Code
' create a float variant Dim v1 As New NVariant(1.5F) ' create a string variant Dim v2 As New NVariant("Value is: ") ' use & operator - res is a string variant with value "Value is: 1.5" Dim res As NVariant = NVariant.op_BitwiseAnd(v2, v1)

Visual Basic

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' create a float variant 
Dim v1 As New NVariant(1.5F)
' create a string variant 
Dim v2 As New NVariant("Value is: ")
' use & operator - res is a string variant with value "Value is: 1.5" 
Dim res As NVariant = NVariant.op_BitwiseAnd(v2, v1)

Explicit Type Change

You can explicitly change the type of a variant with the help of the ChangeType method. This method will appropriately convert the contained value to the new type.