Prevent User From Entering Numbers Or Other Characters Such As $%

Nov 22, 2009

i want to prevent users from entering numbers and other characters such as (_,"*&^$#).... into my textbox-u know what i mean! I want my textbox to accept only alphabets. I have written a function that is able to check the numbers but i don't know how to check whether the text contains those special characters. Here is my code for the numbers. i'm sure, just as i'm able to check the numbers. i'll be able to check for those characters.

Public Function ValidateText(ByVal GetString As String) As Boolean
Dim Count As Integer = GetString.Length
Dim i As Integer



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Mar 26, 2009

The app uses several forms to let the user enter information. In each form the info is entered into textboxes and dealt with elsewhere when the "Enter" button is clicked. A lot if the info entered is used in calculations and so must not contain alpha characters, only numbers. What is the best way of examining each entry and identifying any that are not numbers, so that I can ask the user for a correction with a MsgBox?Prevent Users Entering Letters Instead of Numbers?

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Jun 29, 2010

I am using a database (access) were i am not using a primary key field. I would like to prevent the user from entering records , if certain fields allready exsists.

I would like to check for 3 of the fields. When these 3 fields has been filled previously with the same data as the new data, i want to return a message.

I am looking at the fields txtWeeknumber.text & txtTopic.text & txtSubOutCome.text

Here are some of my


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May 14, 2012

Is there a way to prevent a user from entering data into a ComboBox, rather then selecting, or can anyone suggest a routine to catch and prevent entries so the user can be made aware the they are not acceptable?

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I have a ComboBox with

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How do you stop the user typing ad?

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I have a datagrid with 5 columns.2 of these columns will have data entered into them automatically - depending on the entries of 2 textboxes.I can disable these 2 columns ok.How can I have it so that the tab key doea not enter the cells of these 2 disabled columns. ideally I'd like the tab to enter the cells of the abled columns only.

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Dec 20, 2010

I have a project that uses a number of DataGridView controls. Most of the cells are of the DataGridViewTextBoxCell persuasion. I declare my controls like so:Dim MyCell as DataGridViewCell Later I specify whether they are DataGridViewTextBoxControls or DataGridViewComboBoxCells like so:

MyCell = New DataGridViewTextBoxCell MyCell = New DataGridViewComboBoxCell None of the places in my code require the ability for the users to enter their own values in the Combo Boxes. That is, they are either hard-coded or the values are gathered from other data within the application.

Currently, users can highlight a combo box control defined as shown above and begin typing anything they like. For example, I have one combo box that offers the user a selection of integers between 1 and 9. I can highlight the combo box cell and enter "Hello, World!" if I'd like.What does it take to disable this ability? I'm sure there's a property, but I have yet to find it. I have searched the Internet, and have found only the ability to have user-entered values added to the list and a stream of data-binding tutorials.

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Mar 6, 2011

I have just about completed a .NET project to write a program to randomly select numbers for a Bingo caller. Over the last month or so Ive learned a lot about .NET but heres something that I consider to be odd and maybe one of you guys can offer an opinion.

One of the features of calling Bingo in a small local club is that callers often use little sayings to accompany certain numbers, I expect youve all heard of (say) All the sixes, clickety click for 66 or 5 and 9 the Brighton line for 59 etc. My little program gives an option to incorporate these with a prompt for the caller that can be edited outside of the program. One of these conventional sayings is used when a number is reversed 12 followed by 21 or 45 followed by 54 for example, when the caller might call (say) 1 and 2, one dozen, number 12 And the other way round 2 and 1, twenty one.

So, I programmed in a bit of code to detect this and to over-ride whatever might otherwise have been the quote with And the other way round and set about testing it. Ive been through literally dozens of full 90 calls watching for the occurrence of a reversed number, spent a few hours doing it, and not once has it occurred which is to say the least, unusual.

So, Im wondering about the Rand Function, could it be that it isnt possible for a reversed number to be selected? Just so you know, I randomly pre-select the order of all 90 numbers, I fill each of the 90 elements of an array with a random number first checking that the number selected hasnt already been stored, if it has, I just get the next random number (and check that too of course), but I cant see how that could prevent reversed numbers being selected, especially in light of the fact that frequently it's not the 'next' number that's used.

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Jan 27, 2009

I was testing my program, and tried entering @ into a text box, but it didn't work. Is there any way for this to be allowed to be entered?

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Apr 4, 2011

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Mar 7, 2012

I'm entering 123 into a field and getting 231.It's because I'm formating the text as I change it.

Private Sub txtObject_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtObject.TextChanged txtObject.Text = Format(Val(txtObject.Text), Zformat)
End Sub zformat is "0.0"

Initially the field is "0.0". If I highlight it and type "1" I get "1.0" the cursor is now in front of the "1",I then type "2" and get "21.0" and the cursor is in front of the "1",I then type "3" and get "231.0".

It is because the cursor is in the "wrong" position.Is there a simple way to fix this?

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May 9, 2011

With the shape of really large characters such as numbers and alphabetic characters + others, is there a way to get that shape as a REGION please?Imagine a really fat snake forming the letter S or two rectangles placed together to form a large letter L or a T like the shapes in TETRIS.

1) Does anyone know of anything in VB.Net that can translate such shapes into a System. Drawing.Region or know of a project elsewhere that achieves this please?

2) While I'm on the subject, how would you SCALE UP / DOWN a System.Drawing.Region please? How would you work out the Transform Matrix required please?

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Jun 6, 2011

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Mar 20, 2009

i want to develop a billing software for my net cafe. how to lock the computer before a user entering their name in my Login form?after they entered their name, this form will insert a new data in userLogin table (user_login_name and login_time), and the computer will be available to use.

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Mar 11, 2012

I have a textbox where the user enters their name, however it is possible to enter numbers in textbox, i was wondering if there is a pre existing function that only allows alphabetical characters to be entered?

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Feb 20, 2012

How to prevent textbox to be not accepting numbers in first

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Oct 21, 2009

I've got an app that sometimes stores some decently small numbers, such as 0.000023425. These numbers get loaded up in TextBox controls for users to edit.

Dim number As Double = 0.000023425
someTextBox.Text = number.ToString() ' Shows "2.3425E-05"

As mentioned, the text that shows is 2.3425E-05, which isn't exactly intuitive for the user to see, plus I have numbers even more precise (out to 19 decimal places). I would like the output to be fixed point. Of course I could easily and cleanly do:

number.ToString("F20") ' Shows "0.00002342500000000000"

But then there's an annoying number of zeros left over. So, to fix that, I could do:

number.ToString("#,##0.####################") ' Shows "0.000023425"

Which is what I want, but is there any better way to do it than to have that giant ugly format string there? So, ok, it's not that ugly, but surely there's a different way, right? My goal is to show the raw value being stored in the DB in a friendly way, and I would rather not have to force a format on the number at all.I found that changing the underlying datatype to Decimal solves the issue.

Dim number As Decimal = 0.000023425
someTextBox.Text = number.ToString() ' Shows "0.000023425" instead of "2.3425E-05"

So it sounds like Doubles aren't precise enough to be displayed normally?

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May 3, 2010

have 4 worksheets, need to enabel user to open any 1 by entering date which is name of worksheet?

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Mar 18, 2011

I have a program that allows a user to input numbers from an inputbox and it displays the Total numbers entered, the sum of the numbers entered, and the average of the numbers entered. What I can not seem to find it how to have it display the largest number entered. The code I have so far is,


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Oct 4, 2011

I am making a program, where the user enters 6 numbers in 6 different text boxes, and it displays the larger of those 6 numbers. But I also want to make it where if the user enters a string value (like S for instance) in the text boxes, it gives an message and says "please enter the numbers again" and the user gets to enter the 6 numbers again. But when I do try to do that, it gives an error message saying conversion from "w/e the user entered" to Double is not valid. If the user just enters the numbers, it works fine. However, I am trying to make it if the user does enter non numeric value, it gives a message window and the user can reenter the numbers again.

Here is my code Example


This is where I am trying to use IsNumeric to show a message if a user does not enter a string so the user can renter the numbers again, but when the user does enter a string value (say in textbox 1) it gives me an error message saying conversion from "S" to 'double' is not valid.


Then right here this is where I have my series of ifs statements, this part works fine, it displays the largest numbers of the 6 textboxes every time. Error free.


And do this with variable number 2, 3, 4, 5.

I know there are easier ways to do these with arrays and stuff. But I am not there yet. I am still learning about ifs and stuff.

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Jun 21, 2009

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Dec 15, 2011

I use Visual Basic 2008 with Mysql I have a table article with the following data :

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Apr 1, 2010

How do i validate a field which contain both characters and numbers? For example, I have a field call Item ID and it must be in the form of ABC123 where ABC is the fix characters that will appear in all the Item ID and 123 is the one that will change accordingly.

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Jul 12, 2009

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Mar 17, 2011

I figured there would be some simple way to set up some textboxes to allow ONLY numbers or ONLY characters, however I haven't found an easy way yet.

Is there a simple trick to setting something like this up? And if so, how would I do it?

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Jun 2, 2011

how to validate a text box to accept only alphabets and numbers. no special characters. in i have tried the following code but it doesn't allow numbers but it allows alphabets only

Private Sub TextBox2_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox2.KeyPress
If (Microsoft.VisualBasic.Asc(e.KeyChar) < 65) _
Or (Microsoft.VisualBasic.Asc(e.KeyChar) > 90) _
And (Microsoft.VisualBasic.Asc(e.KeyChar) < 97) _


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Someone may think this is bruteforce hacking, but I don't see why I should do that? If I want to find a password on 13 characters, it would be: 62^13 = 200028539268669788905472 possibilities... in other words... it would take forever!

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Dec 11, 2011

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I need the code to filter the data entered in a textbox. Although it accepts all the characters during runtime, the code should remove all the strings and alpha numeric characters except the numbers (which would be my output). I tried the following code but guess it won't do:

a = Textbox1.text
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Nov 12, 2011

I'm writing a program on CD Collection. My problem is write a code that prevents a user to enter a CD collection name that is already stored in the filename.txt.

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Here's my whole program:

Option Explicit On
Option Strict On
Option Infer Off


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Jul 13, 2009

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Oct 29, 2011

I am writing an application that needs to be running all the time and I don't want the user to be able to close it. I don't want to hide the process from Task Manager. All I need is that when the user tries to terminate the process, he has to enter a password.

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I have the following settings:

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Apr 29, 2010

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i want prevent user order column.i have a datagridview , it has allowuserordercolumns properties and it is set to false. But i didnt see so. i still order can i prevent user ordering column.

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