使用C＃填充文本框后如何启用按钮

Question

As per AntLaC link suggestion I have tried but it is not working in my coding. please help me where i made mistake please let me know. Below is back end code

 protected void txtCardHolderName1_TextChanged(object sender, EventArgs e)
    {
        if (txtCardHolderName1.Text.Length > 0)
        {
            btnNext.Enabled = true;
        }
        else
        {
            btnNext.Enabled = false;
        }
    }

aspx code

 <asp:UpdatePanel ID="upServiceFee" runat="server">
<ContentTemplate>
    <asp:TextBox ID="txtCardHolderName1" runat="server" CssClass="txtbox" Width="220px" ValidationGroup="ServiceFee" MaxLength="100" AutoPostBack="true" AutoCompleteType="Disabled" autocomplete="off" OnTextChanged="txtCardHolderName1_TextChanged"></asp:TextBox>
</ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="btnNext" runat="server" CssClass="btn btnBlue btnStep" Text="Submit" OnClick="btnSubmit_Click" CausesValidation="true"  ValidationGroup="ServiceFee" Enabled="false" />

Answer 1

即使不使用AutoPostBack属性，也可以处理TextChanged事件。

Answer 2

您可以尝试将if语句更改为：

if(textBox != null)

Answer 3

I got My answer with the help of javascript,Thank you so much for helping me. Just i put below code in postback

string var = ClientScript.GetPostBackEventReference(btnNext, "").ToString();
            btnNext.Attributes.Add("onClick", "javascript :if ( Page_ClientValidate() ){this.disabled=true; this.value='Please Wait...';" + var + "};");