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Change border and background color of asp.net controls on validation failure using javascript and CSS

Introduction:  In this article I am going to explain how to highlight i.e. change border and background color of asp.net controls on validation failure using javascript and CSS
Change border and background color of asp.net controls on validation failure using javascript and CSS

Description: We all implement validation on control placed on page and display appropriate messages on validation failure. But to make it more eye catching we can also highlight the invalid controls by changing the border and/or background color of invalid controls.

Implementation: Let’s create a sample page for demonstration purpose.

HTML Source Code
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
        .error {
            background-color: #F9E3E4;
            border: solid 1px Red;
        }
    </style> 
</head>
<body>
    <form id="form1" runat="server">
        <div>
            <table>
                <tr>
                    <td>Name: </td>
                    <td>
                        <asp:TextBox ID="txtName" runat="server"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="rfvName" SetFocusOnError="true" ForeColor="#FF3300" ControlToValidate="txtName"
                            runat="server" ErrorMessage="Required" Display="Dynamic"></asp:RequiredFieldValidator></td>
                </tr> 
                <tr>
                    <td>Country: </td>
                    <td>
                        <asp:DropDownList ID="ddlCountry" runat="server" Width="150px">
                            <asp:ListItem Value="0" Text="--Select--"></asp:ListItem>
                            <asp:ListItem Value="1" Text="USA"></asp:ListItem>
                            <asp:ListItem Value="2" Text="Japan"></asp:ListItem>
                            <asp:ListItem Value="3" Text="India"></asp:ListItem>
                            <asp:ListItem Value="4" Text="China"></asp:ListItem>
                        </asp:DropDownList>
                        <asp:RequiredFieldValidator ID="rfvCountry" ControlToValidate="ddlCountry"
                            runat="server" InitialValue="0" SetFocusOnError="true" ForeColor="#FF3300" ErrorMessage="Required" Display="Dynamic"></asp:RequiredFieldValidator>
                    </td>
                </tr>
                <tr>
                    <td>Email: </td>
                    <td>
                        <asp:TextBox ID="txtEmail" runat="server"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="rfvEmail" ControlToValidate="txtEmail"
                            runat="server" SetFocusOnError="true" ForeColor="#FF3300" Display="Dynamic" ErrorMessage="Required"></asp:RequiredFieldValidator>
                        <asp:RegularExpressionValidator ID="rgeEmail" runat="server" ErrorMessage="Not a valid email" Display="Dynamic" ForeColor="#FF3300" SetFocusOnError="True" ControlToValidate="txtEmail" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator> 
                    </td>
                </tr>
                <tr>
                    <td></td>
                    <td>
                        <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" /></td>
                </tr>
            </table>
        </div>
    </form>
    <script type="text/javascript">
        function WebForm_OnSubmit() {
            if (typeof (ValidatorOnSubmit) == "function" && ValidatorOnSubmit() == false) {
                var prevControl = "";
                for (var i in Page_Validators) {
                    try {
                        var control = document.getElementById(Page_Validators[i].controltovalidate);
                        if (!Page_Validators[i].isvalid) {
                            control.className = "error";
                            prevControl = control;
                        } else {
                            control.className = "";
                        }
                        if (control = prevControl) {
                            control.className = "error";
                        }
                    } catch (e) { }
                }
                return false;
            }
            return true;
        }
    </script>
</body>
</html>

In the Code behind (.aspx.cs/vb) file write the code to be executed on validation pass 
protected void btnSubmit_Click(object sender, EventArgs e)
    {   
    }

Explanation: First in the <head> tag of the page i have created a CSS class “error” to change the border and background color of invalid controls.

Then Just above the closing </body> tag I have used javascript’s  WebForm_OnSubmit method to check and highlight control on validation failure. It is must to place this code just above the closing </body> tag otherwise it will not work.        

Now over to you:
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