Execute Text Box_TextChanged Event in Asp.Net using C#?

Question

I am trying to implement validations on textbox like if null then display a message to fill the empty field and to check the length of the text entered. I have written the code for it inside TextBox_TextChanged event but it's not working. The event is not getting fired and the user can is able to signup without a username, that is my problem at the moment. Do I have to trigger the event manually? Here is a glimpse of what I am doing:

protected void FirstN_TextBox_TextChanged(object sender, EventArgs e)
    {
        String firstNameEntered = FirstN_TextBox.Text;
        if (firstNameEntered != null)
        {
            if (firstNameEntered.Length <= 20)
            {
                MessageBox.Show("Inside text box");
            }
            else
            {

            }

        }
        else
        {
            FirstN_TextBox.Focus();
            MessageBox.Show("Please fill the marked field");
        }

Are you using ASP.NET WebForm? How are you using on the client side (.asp or .aspx files)? I will suggest using JavaScript instead of C# code behind. — RK_Aus
– RK_Aus, Commented Apr 27, 2017 at 3:22
if you are using asp.net this MessageBox.Show can't be done. — Vijunav Vastivch
– Vijunav Vastivch, Commented Apr 27, 2017 at 3:24
@reds I havn't changed anything inside the HTML code but still if you want to see: <asp:TextBox ID="FirstN_TextBox" placeholder="First name" runat="server" Width="225px" OnTextChanged="FirstN_TextBox_TextChanged"></asp:TextBox> — Deep
– Deep, Commented Apr 27, 2017 at 3:41

Vijunav Vastivch · Accepted Answer · 2017-04-27 03:49:42Z

2

change it like this:

From:

<asp:TextBox ID="FirstN_TextBox" placeholder="First name" runat="server" Width="225px"   OnTextChanged="FirstN_TextBox_TextChanged"></asp:TextBox>

To:

 <asp:TextBox ID="FirstN_TextBox" placeholder="First name" runat="server" Width="225px"   OnTextChanged="FirstN_TextBox_TextChanged" AutoPostBack ="true"></asp:TextBox>

answered Apr 27, 2017 at 3:49

Vijunav Vastivch

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6 Comments

Vijunav Vastivch Over a year ago

Clean and build your project after you change it.

Deep Over a year ago

I have done the same but still validation not working.

Vijunav Vastivch Over a year ago

Its tested before i post. don't know what you did. try to check spaces and remove

Deep Over a year ago

I have done exactly the same but didn't work. So I switched to validate controls. But I appreciate your time and efforts. Thanks.... :)

Vijunav Vastivch Over a year ago

do you want to try keypress event?

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