CODEWITHSUNDEEP
c#asp.netregexvalidationtextbox
codeN00b
codeN00b

Reputation: 23

How do I validate a TextBox with a RegularExpression based on a DropDownList Selection?

I would like validate a Textbox based on a Dropdown List with regular expression. I would like to validate a credit card number based on the card type selected by the dropdown list.

Here is a sample of my code:

<table runat="server">
<tr>
    <td><asp:Label ID="Label4" runat="server" Text="Credit Card Type"></asp:Label></td>
    <td><asp:DropDownList ID="DropDownList1" runat="server">
            <asp:ListItem Text="Visa" Value="Visa"></asp:ListItem>
            <asp:ListItem Text="MasterCard" Value="Mastercard"></asp:ListItem>
        </asp:DropDownList></td>
</tr>
<tr>
    <td><asp:Label ID="Label1" runat="server" Text="Card Number"></asp:Label></td>
    <td><asp:TextBox ID="TextBox1" runat="server"></asp:TextBox></td> 
    <td><asp:CustomValidator ID=CustomValidator1 runat="server" ErrorMessage="Incorrect card, please re-renter!" ControlToValidate="TextBox1" Display="Dynamic" ForeColor="Red" OnServerValidate="CustomValidator1_ServerValidate"></asp:CustomValidator></td>      
</tr>
<tr>
    <td><asp:Button ID="Button1" runat="server" Text="Submit" CommandName="Submit"/></td>
</tr>
</table>

And my other code:

protected void CustomValidation1_ServerValidate(object Source, ServerValidateEventArgs args)
{
    string expression = "";

    switch (DropDownList.SelectedValue)
    {
        case "Visa":
        expression = "^(4)([0-9]{15})$";
        break;
        case "MasterCard":
        expression = "^(5[1-5])([0-9]{14})$";
        break;
    }
}

So when I select on MasterCard on the Dropdown List and input numbers in the textbox. I would like to be validate with the regular expression ^(5[1-5])([0-9]{14})$. And also when I select Visa on the Dropbox List and input numbers in the textbox, it will validate with the expression of ^(4)([0-9]{15})$.

Here it would be for MasterCard:

Matches: 5212345678901234

Does not Match: 1234567890123456

Upvotes: 2

Views: 1657

Answers (2)

blobs
blobs

Reputation: 86

What you can do would be as follows:

Instead of a custom validator, you will need to add a regular expression validator at the end of the textbox and with the process of code behind for your drop down list, use if statements that will allow the change to persist. Also your drop down list needs to perform Auto Post Back setting to True to allow the changes to occur.

Here is the ideal code behind for your question:

protected void DropDownList1_OnIndexChanged(object Source, EventArgs args)
{


    if (DropDownList.SelectedItem.Text == "Visa")
    {
        RegularExpression1.ValidationExpression = "^(4)([0-9]{15})$";
        else
        RegularExpression1.ValidationExpression = "^(5[1-5])([0-9]{14})$";
    }
}

Upvotes: 1

Mikhail Timofeev
Mikhail Timofeev

Reputation: 2169

I would do it so:

Declare 2 RegExpValidators one for VISA-Regex, another for MasterCard-Regex. Declare OnSelectedIndexChanged-Method for the DropDownList in code behind. In this method enable the correct validator based on the SelectedValue of the DropDownList and disable the onother one.

Upvotes: 0

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