Type conversion functions

아티클
08/01/2023

Each function coerces an expression to a specific data type.

Syntax

CBool(expression)
CByte(expression)
CCur(expression)
CDate(expression)
CDbl(expression)
CDec(expression)
CInt(expression)
CLng(expression)
CLngLng(expression) (Valid on 64-bit platforms only.)
CLngPtr(expression)
CSng(expression)
CStr(expression)
CVar(expression)

The required expression argument is any string expression or numeric expression.

Return types

The function name determines the return type as shown in the following:

Function	Return type	Range for expression argument
CBool	Boolean	Any valid string or numeric expression.
CByte	Byte	0 to 255.
CCur	Currency	-922,337,203,685,477.5808 to 922,337,203,685,477.5807.
CDate	Date	Any valid date expression.
CDbl	Double	-1.79769313486231E308 to -4.94065645841247E-324 for negative values; 4.94065645841247E-324 to 1.79769313486232E308 for positive values.
CDec	Decimal	79,228,162,514,264,337,593,543,950,335 for zero-scaled numbers, that is, numbers with no decimal places. For numbers with 28 decimal places, the range is 7.9228162514264337593543950335. The smallest possible non-zero number is 0.0000000000000000000000000001.
CInt	Integer	-32,768 to 32,767; fractions are rounded.
CLng	Long	-2,147,483,648 to 2,147,483,647; fractions are rounded.
CLngLng	LongLong	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807; fractions are rounded. (Valid on 64-bit platforms only.)
CLngPtr	LongPtr	-2,147,483,648 to 2,147,483,647 on 32-bit systems, -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 on 64-bit systems; fractions are rounded for 32-bit and 64-bit systems.
CSng	Single	-3.402823E38 to -1.401298E-45 for negative values; 1.401298E-45 to 3.402823E38 for positive values.
CStr	String	Returns for CStr depend on the expression argument. See the following table.
CVar	Variant	Same range as Double for numerics. Same range as String for non-numerics.

Remarks

If the expression passed to the function is outside the range of the data type being converted to, an error occurs.

Note

Conversion functions must be used to explicitly assign LongLong (including LongPtr on 64-bit platforms) to smaller integral types. Implicit conversions of LongLong to smaller integrals are not allowed.

In general, you can document your code using the data-type conversion functions to show that the result of some operation should be expressed as a particular data type rather than the default data type. For example, use CCur to force currency arithmetic in cases where single-precision, double-precision, or integer arithmetic normally would occur.

You should use the data-type conversion functions instead of Val to provide internationally aware conversions from one data type to another. For example, when you use CCur, different decimal separators, different thousand separators, and various currency options are properly recognized depending on the locale setting of your computer.

When the fractional part is exactly 0.5, CInt and CLng always round it to the nearest even number. For example, 0.5 rounds to 0, and 1.5 rounds to 2. CInt and CLng differ from the Fix and Int functions, which truncate, rather than round, the fractional part of a number. Also, Fix and Int always return a value of the same type as is passed in.

Use the IsDate function to determine if date can be converted to a date or time. CDate recognizes date literals and time literals as well as some numbers that fall within the range of acceptable dates. When converting a number to a date, the whole number portion is converted to a date. Any fractional part of the number is converted to a time of day, starting at midnight.

CDate recognizes date formats according to the locale setting of your system. The correct order of day, month, and year may not be determined if it is provided in a format other than one of the recognized date settings. In addition, a long date format is not recognized if it also contains the day-of-the-week string.

A CVDate function is also provided for compatibility with previous versions of Visual Basic. The syntax of the CVDate function is identical to the CDate function; however, CVDate returns a Variant whose subtype is Date instead of an actual Date type. Since there is now an intrinsic Date type, there is no further need for CVDate. The same effect can be achieved by converting an expression to a Date, and then assigning it to a Variant. This technique is consistent with the conversion of all other intrinsic types to their equivalent Variant subtypes.

Note

The CDec function does not return a discrete data type; instead, it always returns a Variant whose value has been converted to a Decimal subtype.

Returns for CStr depend on the expression argument.

If expression is	CStr returns
Boolean	A string containing True or False.
Date	A string containing a date in the short date format of your system.
Empty	A zero-length string ("").
Error	A string containing the word Error followed by the error number.
Null	A run-time error.
Other numeric	A string containing the number.

CBool function example

This example uses the CBool function to convert an expression to a Boolean. If the expression evaluates to a nonzero value, CBool returns True, otherwise, it returns False.

Dim A, B, Check 
A = 5: B = 5 ' Initialize variables. 
Check = CBool(A = B) ' Check contains True. 
 
A = 0 ' Define variable. 
Check = CBool(A) ' Check contains False.

CByte function example

This example uses the CByte function to convert an expression to a Byte.

Dim MyDouble, MyByte 
MyDouble = 125.5678 ' MyDouble is a Double. 
MyByte = CByte(MyDouble) ' MyByte contains 126.

CCur function example

This example uses the CCur function to convert an expression to a Currency.

Dim MyDouble, MyCurr 
MyDouble = 543.214588 ' MyDouble is a Double. 
MyCurr = CCur(MyDouble * 2) ' Convert result of MyDouble * 2 
 ' (1086.429176) to a 
 ' Currency (1086.4292).

CDate function example

This example uses the CDate function to convert a string to a Date. In general, hard-coding dates and times as strings (as shown in this example) is not recommended. Use date literals and time literals, such as #2/12/1969# and #4:45:23 PM#, instead.

Dim MyDate, MyShortDate, MyTime, MyShortTime 
MyDate = "February 12, 1969" ' Define date. 
MyShortDate = CDate(MyDate) ' Convert to Date data type. 
 
MyTime = "4:35:47 PM" ' Define time. 
MyShortTime = CDate(MyTime) ' Convert to Date data type.

CDbl function example

This example uses the CDbl function to convert an expression to a Double.

Dim MyCurr, MyDouble 
MyCurr = CCur(234.456784) ' MyCurr is a Currency. 
MyDouble = CDbl(MyCurr * 8.2 * 0.01) ' Convert result to a Double.

CDec function example

This example uses the CDec function to convert a numeric value to a Decimal.

Dim MyDecimal, MyCurr 
MyCurr = 10000000.0587 ' MyCurr is a Currency. 
MyDecimal = CDec(MyCurr) ' MyDecimal is a Decimal.

CInt function example

This example uses the CInt function to convert a value to an Integer.

Dim MyDouble, MyInt 
MyDouble = 2345.5678 ' MyDouble is a Double. 
MyInt = CInt(MyDouble) ' MyInt contains 2346.

CLng function example

This example uses the CLng function to convert a value to a Long.

Dim MyVal1, MyVal2, MyLong1, MyLong2 
MyVal1 = 25427.45: MyVal2 = 25427.55 ' MyVal1, MyVal2 are Doubles. 
MyLong1 = CLng(MyVal1) ' MyLong1 contains 25427. 
MyLong2 = CLng(MyVal2) ' MyLong2 contains 25428.

CSng function example

This example uses the CSng function to convert a value to a Single.

Dim MyDouble1, MyDouble2, MySingle1, MySingle2 
' MyDouble1, MyDouble2 are Doubles. 
MyDouble1 = 75.3421115: MyDouble2 = 75.3421555 
MySingle1 = CSng(MyDouble1) ' MySingle1 contains 75.34211. 
MySingle2 = CSng(MyDouble2) ' MySingle2 contains 75.34216.

CStr function example

This example uses the CStr function to convert a numeric value to a String.

Dim MyDouble, MyString 
MyDouble = 437.324 ' MyDouble is a Double. 
MyString = CStr(MyDouble) ' MyString contains "437.324".

CVar function example

This example uses the CVar function to convert an expression to a Variant.

Dim MyInt, MyVar 
MyInt = 4534 ' MyInt is an Integer. 
MyVar = CVar(MyInt & 000) ' MyVar contains the string 
 ' 4534000.

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