String Functions Explained

Tuesday Nov 19th 2002 by John Percival
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String Functions Explained

Visual Basic provides several functions to format and retrieve parts of strings.

Joining strings with &

You can use the & operator to join two strings. This operation is called concatenation. For example:

FirstString = "This string has "
SecondString = "been concatenated!"
NewString = FirstString & SecondString

NewString would contain "This string has been concatenated!". Note that you need a space at the end of the first string or at the beginning of the second string, so that there is a space between "has" and "been".

Left$, Right$

These functions retrieve part of the string. The Left$ function returns characters from the left hand side, and the Right$ function returns characters from the right hand side. This is what they do:

MyString = "This is a nice long string"
LeftString = Left$(MyString, 7)
RightString = Right$(MyString, 6)

LeftString contains the text "This is", and RightString contains the text "string".

Syntax

Left$(string, length)
Right$(string, length)

Mid$

This function is used to retrieve part of a string, much like Left$ and Right$. This is how it is used:

MyString = "This is a nice long string"
NewString = Mid$(MyString, 6, 21)

NewString now contains "is a nice long string"

Syntax

Mid(string, start[, length])

UCase$, LCase$

Use these two functions to convert a string to entirely upper case or entirely lower case characters. This is very useful if you want to do a case insensitive search, or if a password is not case sensitive. For example:

MyString = "This is a nice long string"
UCaseString = UCase$(MyString)
LCaseString = LCase$(MyString)

UCaseString contains "THIS IS A NICE LONG STRING", and LCaseString contains "this is a nice long string". This can be used practically:

PasswordAttempt = "MyPaSs"
ActualPassword = "mYpAsS"If PasswordAttempt = _
      ActualPassword Then succeeded1 = True 
Else 
   succeeded1 = False
End If

If UCase$(PasswordAttempt) = UCase$(ActualPassword) _
   Then succeeded2 = True 
Else 
   succeeded2 = False
End If

In this case, succeeded1 would be False, and suceeded2 would be True. This is because the two actual passwords do not equal each other, but when they are both converted into upper case, they do equal each other.

Syntax

Mid(string, start[, length])

String$

This function returns a string of repeating characters. For example, String$(20, "*"), would return "********************".

Syntax

String(number, character)

Len

This function returns the length of a string. It is useful in a For...Next loop to do something to each character in a string. For example:

mystring = "Hello world!"
mylen = Len(mystring)
For charnum = 1 To mylen
Debug.Print Mid$(mystring, charnum, 1)
Next

Here you will get H, e, l, l, o, , w, o, r, l, d, !, printed out in the debug widow, with each character on a separate line. mylen returns 11 because the length of the string is 11.

Syntax

Len(string)

Watch out soon for advanced string functions, where we will show you how to do search and replace facilities, and look at the other string functions. 

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