How to write regex for "at least 50 symbols"?

I 开发者_运维问答need regex for Regular Expression Validator in ASP.NET, that user need to write in message at least 50 symbols(characters). How to do it? I tried

.(dot){50,} but it doesn't work.

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.{50,} seems a correct RegExp to me.

However, I think, the regular expression is only checked if the field is not empty, and empty strings are considered valid, so you need to couple this with a RequiredFieldValidator.

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This one should work.

<asp:RegularExpressionValidator ID="Validator1" runat="server" 
 ControlToValidate="TextBox"
 ErrorMessage="Minimum length is 50"
 ValidationExpression=".{50}.*" />

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This works for me

/^[a-zA-Z0-9]{50,}$/