How can I Prevent users to put special characters in a TextBox

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I want to prevent users from entering Special characters like " ,' etc in a TextBox.
Textbox is a search box which can accept names only (a to z and 0-9 only).

I want to use a Custom validator but no idea what to put in C# code.

How can I do it?

*********

VB

<asp:CustomValidator ID="CustomValidator1" runat="server"
                    ControlToValidate="SearchTextBox"
                    ErrorMessage="Special Characters are not allowed"
                    onservervalidate="CustomValidator1_ServerValidate" />

************

C#

protected void ServerValidate(object sender, ServerValidateEventArgs e)
{
   //need code here.
}

Thanks..

Posted 7-Oct-13 11:51am

Coldcreek

Updated 8-Oct-13 7:07am

v5

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Sergey Alexandrovich Kryukov 7-Oct-13 18:04pm

There is no such thing as "special character", is there? What's so "special" in ','?
—SA

Coldcreek 7-Oct-13 18:06pm

Like Quotation mark (") in search box.
Say you put the name "Peter" .
I want users to put only Peter (no quotations mark)

Thanks

Sergey Alexandrovich Kryukov 7-Oct-13 18:13pm

Whatever it is, you need to strictly and comprehensively define your character sets, without any examples. Anyway, I answered, please see.
—SA

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Jeewiz2 · Accepted Answer · 2013-10-07T12:37:00

For any alphanumeric requirements in a textbox I use the built in validator with an extention for popup window using the ajaxtoolkit.

<asp:TextBox ID="txtID" runat="server" Width="50%" MaxLength="10"></asp:TextBox>
<asp:Label ID="lblRequiredFieldIndicator0" runat="server" Font-Bold="True" ForeColor="Red" Text="*"></asp:Label>
<asp:RegularExpressionValidator ID="regExID" ForeColor="Red" runat="server" Height="24px" Width="192px" ControlToValidate="txtID" Display="None" ValidationExpression="^[0-9a-zA-Z-]+$" ErrorMessage="Only Alphanumeric characters"></asp:RegularExpressionValidator>
<ajaxToolkit:ValidatorCalloutExtender runat="Server" ID="vceRegExID" TargetControlID="regExID" HighlightCssClass="validatorCalloutHighlight" Width="250px" />
<asp:RequiredFieldValidator runat="server" ID="reqID" ControlToValidate="txtID" Display="None" ErrorMessage="<b>Required Field Missing</b><br />No Special Characters allowed." />
<ajaxToolkit:ValidatorCalloutExtender runat="Server" ID="vceID" TargetControlID="reqID" HighlightCssClass="validatorCalloutHighlight" Width="250px" />

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-10-07T12:11:00

I don't understand your problem with C#. For any character ch you, can easily check if it is an element of some set of "bad" characters, or it can be found in a set of the "good" characters:

C#

if (System.Char.IsLetter(ch) || System.Char.IsDigit(ch)) //... good one

// or

string badCharacters = ".;*?^&"; // whatever
if (badCharacters.Contains(ch)) //... bad one

// or, you can limit "good" characters by just Latin and digits...

However, if you want to constraint the character input in, say, text box, you should better not do it in C#, because on every input you will have a postback which would slow down things beyond anything tolerable. Then you need to have a JavaScript filtering out key presses based on the character code point. This is easy enough, too.

—SA

How can I Prevent users to put special characters in a TextBox

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