AllAPI Network - The KPD-Team

 
Allapi Network
 API-Guide
 ApiViewer

 API List

 
API Resources
 Tips & Tricks
 VB Tutorials
 Error Lookup
 
Misc Stuff
 VB examples
 VB Tools
 VB Links
 Top Downloads
 
This Site
 Search Engine
 Contact Form
 

Donate to AllAPI.net

Programming in Visual Basic

String Functions :

A string is a set of characters treated as a single object. A string can inlude letters, numbers and special characters such as -,,&,*,etc. The following are typical types of string:

A name

Freda Bloggs

A telephone number

0121-743-4471

A date

16-1-99

A time

22:05

A number

345

Anything you like

45$%&ER(787***)

Everything entered in a text box is treated as a string and, as we saw in an earlier unit, numeric strings needed to be changed to values for use within calculations. The val function we use to do this is a typical example of a string function. Some of the other typical string functions are outlined below.

LCase or UCase :

The LCase statement will turn an entire string into lower case, UCase turns a string into upper case. For example:

txtItem

LCase(txtItem)

UCase(txtItem)

Radio

radio

RADIO

Disk 3.5

disk 3.5

DISK 3.5

By checking everything as upper case or lower case, we do not need to worry how the end user enters the information. For example, the first section of the Find Item code within the Stock project would change as follows:

Sub cmdFindItem_Click()
   If UCase(txtItem) = "RADIO" Then
      txtPrice = 12.54
   End If
End Sub

Left or Right :

The Left and Right functions are used to look at a set number of characters at the beginning or end of a string. The format is Left(String, Number of characters). For example:

txtItem

Left(txtItem, 5)

Right(txtItem, 3)

Radio Set

Radio

Set

Visual Basic

Visua

sic

Mid :

The Mid function return a certain number of characters from inside a string. The format is Mid(String, Starting Point, Number of Characters). For example:

txtItem

Mid(txtItem, 4, 5)

Mid(txtItem, 8, 1)

Radio Set

io Se

e

Visual Basic

ual B

B

InStr :

The Instr function tests to see whether on string occurs within another string. If the string occurs, the position of the start of the string is returned, otherwise 0 is returned. A start point for the search can be included, but is not compulsory. The format is InStr(Start Point, Large string, Small String). For example:

txtItem

Instr(1, txtItem, "Brown")

Instr(1, txtItem, "Smith")

Paul Brown

6

0

The Instr function is particulary useful for complex fields when the user may not give exactly what we expect. For example, suppose the user enters a full namewithin the Address project, we could use the following code as part of the Find Name code:

If Instr(txtName, "Brown") > 0 Then
   txtAddress1 = .........
   ...
   ...
   ...
End If

Mixing String Functions :

Quite often we mix string functions to ensure thorough checking. For example, we might need to force upper case for checking purposes and only look at a certain number of characters. Here are some examples:

If Right(UCase(txtItem), 5) = "RADIO" Then ...
If InStr(1, UCase(txtName), "BROWN") > 0 Then ...

Format :

The format function is used to change the format of string, particularly those containing values. The general format is Format(String, format string). The format string is a set of characters that define how the string will be displayed. Typical format characters are

0

Display a digit ar a zero

#

Display a digit or nothing (if zero)

%

Multiply by 100 and add the % character

Insert a character

-() space

Display -,(,) or a space

For example:

String

Format String

Result

23.4567

"0000.00"

0023.46

23.4567

"####.##"

23.46

23.4567

"0000.00"

0023.46

23.4567

"####.##"

23.46

01217434471

(0000) 000 0000

(0121) 743 4471

Exercise Ten :

For all of the following, test that your code works before continuing.

1. Open the Stock project

2. Edit the coding of the Find Item command button and use the Ucase or LCase function to ensure correct matching.

3. Add the left function to only check the amount of characters that should have been entered i.e. for "Radio", check Left(txtItem, 5).

4. Add an extra button that will allow the user to search for part of a string (e.g. "Set" within "Dinner Set"). Copy the code from th Find Item button and paste into the code for the new button. Amend the code to use the InStr function.

5. Edit the code for the Calculate button to make use of the Format function to display the Sub Total, VAT and Total Price as currency.

6. Open the Address project.

7. Amend the code for the Find Name button to make use of the InStr function to find either the first name or last name.

8. Use the format function to display the telephone number as follows:
0121-7434471

9. Amend the code for the Find Telephone button to allow for the fact that the user may enter the number without the area code. (InStr or Right could be used).

10. The Len function ( Len(string) ) returns the number of characters in a string. Assume that a telephone number cannot have more than 12 characters. Add a test to the Find Telephone code to check that the user's number is not too big.

11. Find out about the Now function and Date formats from th help menu. Add a text box to all your forms that displays today's date in a suitable format.

Page [<< PREV] 1 2 3 4 5 6
Back to Tutorials - Main

 

 


Copyright © 1998-2007, The Mentalis.org Team - Privacy statement
Did you find a bug on this page? Tell us!
This site is located at http://allapi.mentalis.org/