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Editorial Team
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Asked: 2026-05-16T22:47:11+00:00

I am using ASP.NET 4. I would like check the length for a string

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I am using ASP.NET 4.

I would like check the length for a string inserted in a TextBox. Ex: Input Name no more than 255 characters.

My questions:

  • Which Web Controls for Validation I can use in ASP.NET?
  • Web Controls for Validation validate both Client side and server side? I mean without Java script enabled the Control is able to validate (on server side)?

Thanks for your time

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1 Answer

  1. Editorial Team

    You can combine the MaxLength property of the text box for user convenience, and the RegularExpressionValidator for client and server-side validation.

    <asp:TextBox ID="textbox" runat="server" MaxLength="255" />
<asp:RegularExpressionValidator ID="regtext" runat="server"
    ControlToValidate="textbox"
    ValidationExpression="^.{0,255}$" />

    If client-side validation fails, a postback is prevented. If javascript is disabled, or your client is an attacker, validation still occurs on the server side.

    To query the page on the server-side to see if validation succeeded, check the IsValid property on the page, and take action accordingly.

    You can check out this resource for an example of IsValid usage.

    http://msdn.microsoft.com/en-us/library/system.web.ui.page.isvalid.aspx

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