Each function coerces an expression (expression: Any combination of mathematical or logical operators, constants, functions, and names of fields, controls, and properties that evaluates to a single value. Expressions can perform calculations, manipulate characters, or test data.) to a specific data type (data type: The characteristic of a field that determines what type of data it can hold. Data types include Boolean, Integer, Long, Currency, Single, Double, Date, String, and Variant (default).).
The required expression argument (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.) is any string expression (string expression: An expression that evaluates to a sequence of contiguous characters. Elements of the expression can be: functions that return a string or a string Variant (VarType 8); a string literal, constant, variable, or Variant.) or numeric expression (numeric expression: Any expression that evaluates to a number. The expression can be any combination of variables, constants, functions, and operators.).
The function name determines the return type as shown in the following:
||Range for expression argument
||Any valid string or numeric expression.
||0 to 255.
||-922,337,203,685,477.5808 to 922,337,203,685,477.5807.
||Any valid date expression.
-4.94065645841247E-324 for negative values; 4.94065645841247E-324 to 1.79769313486232E308 for positive values.
||+/-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.
||-32,768 to 32,767; fractions are rounded.
||-2,147,483,648 to 2,147,483,647; fractions are rounded.
||-3.402823E38 to -1.401298E-45 for negative values; 1.401298E-45 to 3.402823E38 for positive values.
||Returns for CStr depend on the expression argument.
||Same range as Double for numerics. Same range as String for non-numerics.
If the expression passed to the function is outside the range of the data type being converted to, an error occurs.
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 (locale: The set of information that corresponds to a given language and country.) 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.
Note Examples that follow demonstrate the use of this function in a Visual Basic for Applications (VBA) module. For more information about working with VBA, select Developer Reference in the drop-down list next to Search and enter one or more terms in the search box.
Tip The Expression Builder with IntelliSense in Access 2010 helps with getting your expressions right. Read an article or try Office 2010.
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.
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.
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).
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"
' Convert to Date data type.
MyShortDate = CDate(MyDate)
MyTime = "4:35:47 PM"
' Convert to Date data type.
MyShortTime = CDate(MyTime)
This example uses the CDbl function to convert an expression to a Double.
Dim MyCurr, MyDouble
MyCurr = CCur(234.456784)
' Convert result to a Double.
MyDouble = CDbl(MyCurr * 8.2 * 0.01)
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.
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.
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.
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.
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".
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.