beginning .net : Set maximum characters allowed for Single Line and Multi Line Textbox in .Net

 Click Here to Download TextBoxMaximumLengthApplication.zip

There is always a need of application to set maximum length allowed in textbox.
In this article we demonstrate both single line textbox and multi line textbox max length validation. 
There is a different way to set maximum characters allowed for single line textbox and multiline textbox.
You can set "MaxLength" property for single line textbox.

 For multiline textbox "MaxLength" does not supported.

So for Multi Line textbox we need some tricky approch. We can use javascript , JQuery or server side checking. Here we are going to use .Net Validator controls. We are using "RegularExpressionValidator" control.

Here is example for this.

In this example we are taking two textbox one is for ProdutTitle which is singleline textbox and other is for ProductDescription which is MultiLine textbox. For ProductTitle we are using MaxLength property to set maximum allowed characters. Which is 20 characters.
For ProductDescription we are using "RegularExpressionValidator" control to set maximum allowed characters. Which is 50 characters.
We are using Regex expression for validation.
The "RegularExpressionValidator" control display error message after typing in textbox focus or cursor moved out from textbox.
You can also make server side validation check for regular expression validation using "Page.Validate()" Method and "Page.IsValid" property.

In output you can see that if more than maximum allowed characters type in textbox it will give error message. You can also make you customize message.


ASPX Code:

        <table>
            <tr>
                <td>
                    Product Title :
                </td>
                <td>
                    <asp:TextBox runat="server" ID="txtProductTitle" MaxLength="20" ></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>
                    Product Description :
                </td>
                <td>
                    <asp:TextBox runat="server" ID="txtProductDescription"  TextMode="MultiLine"></asp:TextBox>
                    <asp:RegularExpressionValidator runat="server" ID="REVProductDescription" ControlToValidate="txtProductDescription"
                        ValidationExpression="^[\s\S]{0,50}$" style="color:Red;font-weight:bold" ErrorMessage="Please enter a maximum of 50 characters"
                        Display="Dynamic"></asp:RegularExpressionValidator>
                </td>
            </tr>
        </table>

Output : 

 

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