How to stop user from entering xml characters

I have a web page that a user can enter in text in a text box.  I want to let the user enter any valid character that does not cause problems when the text is put into xml.

So I want to stop the user from entering in anything that would cause XML to have a problem.  Some of the characters are <, & and so forth.  I don't know what they all are.

If the user enters any of these in, I want to stop them and show an error.  I was wanting to use reqular expressions to do this if possible.

Thanks for your help.
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RandymarAsked:
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käµfm³d 👽Commented:
Try searching for these:

['"&<>]

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If you used a RegularExpressionValidator, then you could do something like:
<asp:RegularExpressionValidator id="RegularExpressionValidator1" 
                                ControlToValidate="TextBox1"
                                ValidationExpression="^[^'&quot;&amp;&gt;&lt;]*$"
                                ErrorMessage="Invalid characters."
                                runat="server"/>

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RandymarAuthor Commented:
I created a Regular Expression to handle this and added the RegularExpressionValidator to add this to my web page.  I also limited the entry to 50 characters.  And then only allowed the user to use only certain special characters.

The Regular expression I used is :  ^([a-zA-Z0-9@*#!]{1,50})$

Thanks kaufmed for your help, I used your suggestion and fashioned what I wanted.
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RandymarAuthor Commented:
Thanks for your help on this.
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Regular Expressions

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