Set Maximum length for multiline textbox in asp.net

In this post we will discuss how we can set maximum length for multiline textbox in asp.net using regular expression validator.

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To make a textbox as multiline textbox we need to add the property as  TextMode="MultiLine".

In case of Single line textbox, you can set the maximum length by setting a value for the property as MaxLength as MaxLength="10".

For multiline of textbox we can use a regular expression and the regular expression will be:

ValidationExpression="^[\s\S]{0,20}$"

.Aspx Code:
<div>
            Text:
            <asp:TextBox ID="txtMultiline" runat="server" TextMode="MultiLine" Height="69px" Width="302px"></asp:TextBox><br />
            <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ValidationExpression="^[\s\S]{0,20}$" ErrorMessage="Can not enter more than 20 characters" ForeColor="Red" ControlToValidate="txtMultiline"></asp:RegularExpressionValidator>
        </div>

Once you will set the regular expression, if you put more than 20 characters, it will appear like below: