Programming Tutorials

Converting between Data Types in VB.net

By: Steven Holzner  

Take a look at this code:

Option Strict On
Module Module1
    Sub Main()
        Dim dblData As Double
        Dim intData As Integer
        dblData = 3.14159
        intData = dblData
        System.Console.WriteLine("intData = " & Str(intData))
    End Sub

End Module

In this case, I've turned Option Strict on, which means that Visual Basic will not automatically convert data types when you assign a value of one type to a variable of another, so it'll have problems with the statement highlighted above, where I assign a double precision floating point variable to an integer variable. To fix this problem, I have to do a specific type conversion. I do this with the CInt function, which converts its argument to type Integer:

Option Strict On
Module Module1
    Sub Main()
        Dim dblData As Double
        Dim intData As Integer
        dblData = 3.14159
        intData = CInt(dblData)
        System.Console.WriteLine("intData = " & Str(intData))
    End Sub

End Module

When I run this code, I get this result—notice that the decimal places have been removed to make the value of pi into an integer:

intData =  3
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Here's the list of conversion functions you can use:

• CBool— Convert to Bool data type.

• CByte— Convert to Byte data type.

• CChar— Convert to Char data type.

• CDate— Convert to Date data type.

• CDbl— Convert to Double data type.

• CDec— Convert to Decimal data type.

• CInt— Convert to Int data type.

• CLng— Convert to Long data type.

• CObj— Convert to Object type.

• CShort— Convert to Short data type.

• CSng— Convert to Single data type.

• CStr— Convert to String type.

If you can't remember the name of a particular conversion function, you also can use the CType function, which lets you specify a type to convert to. (This is useful if you're converting to a type that is not one of the simple types in the list above.):

Option Strict On
Module Module1
    Sub Main()
        Dim dblData As Double
        Dim intData As Integer
        dblData = 3.14159
        intData = CType(dblData, Integer)
        System.Console.WriteLine("intData = " & Str(intData))
    End Sub
End Module

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