4
I’m having a mistake that came to nothing, I’m two days trying a solution to the same and so far unsuccessful.
I have a form all made in webforms that when clicking the button to send the data is generated the following error.
<%@Page Title="" Language="C#" MasterPageFile="~/MasterPage.Master" AutoEventWireup="true" CodeBehind="Delivery_automatic.aspx.cs" Inherits="UI.Delivery_automatic" EnableEventValidation="true"  %>
<!doctype html>
<%--<html xmlns="http://www.w3.org/1999/xhtml">--%>
<%--ANGULAR JS--%>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>DELIVERY_AUTOMATIC</title>
    <%--Colocar esse script em um arquivo único --%>
    <%--somente numeros--%>
    <script type="text/javascript">
        var specialKeys = new Array();
        specialKeys.push(8); //Backspace
        function IsNumeric(e) {
            var keyCode = e.which ? e.which : e.keyCode
            var ret = ((keyCode >= 48 && keyCode <= 57) || specialKeys.indexOf(keyCode) != -1);
            document.getElementById("error").style.display = ret ? "none" : "inline";
            return ret;
        }
        //usando datepicker no textbox
        <%--            $(function () {
            $("#<%= data.ClientID %>").datepicker();
        });--%>
    </script>
</head>
<body>
    <div class="container">
        <div style="text-align: center;">
            <div class="well well-sm">
                <asp:Label ID="TITULO" runat="server" Text="ENTREGA AUTOMÁTICA" Font-Bold="true" ForeColor="Red"></asp:Label>
            </div>
        </div>
    </div>
    <div class="col-md-1">
    </div>
    <div class="panel panel-primary col-md-3">
        <form runat="server" visible="true">
            <table class="table table-reflow">
                <tbody>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Cliente:</span>                            
                            <asp:DropDownList ID="DropLabs" runat="server" DataSourceID="DataLabs" DataTextField="LAB" DataValueField="COD_LAB"  AppendDataBoundItems="True" Width="155px" AutoPostBack="true">
                                <asp:ListItem Value="0" Selected="True">---</asp:ListItem>
                            </asp:DropDownList>
                            <asp:SqlDataSource ID="DataLabs" runat="server" ConnectionString="Data Source=S-CUPBR04;Initial Catalog=DMD_Portal;Persist Security Info=True;User ID=dmddeveloper;Password=dmddeveloper" ProviderName="System.Data.SqlClient" SelectCommand="SELECT [COD_LAB], [LAB] FROM [LABS]"></asp:SqlDataSource>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Código Cliente:</span>                     
                            <asp:TextBox ID="codcli" runat="server" Enabled="false" Width="150px"></asp:TextBox>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Nome entrega:</span>
                            <asp:DropDownList ID="DropJobname" runat="server" DataSourceID="DataEntrega" DataTextField="JOBNAME" DataValueField="JOBNAME" Width="120px">
                            </asp:DropDownList>
                            <asp:SqlDataSource ID="DataEntrega" runat="server" ConnectionString="<%$ ConnectionStrings:DMD_DEPLOYConnectionString %>" SelectCommand="SELECT JOBNAME FROM SysHive.dbo.AUTODOWN_JOBLIST"></asp:SqlDataSource>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Periodicidade:</span>
                            <asp:DropDownList ID="DropPeriodic" runat="server" Width="150px">
                                <asp:ListItem Value="D">Diário</asp:ListItem>
                                <asp:ListItem Value="W">Semanal </asp:ListItem>
                                <asp:ListItem Value="M">Mensal </asp:ListItem>
                            </asp:DropDownList>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Data:</span>
                            <input type="text" id="datepicker" name="inputdate" required=""/>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Email Cliente:</span>
                            <asp:TextBox ID="email" runat="server" Width="150px"></asp:TextBox>
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Pasta Download:</span>
                            <asp:FileUpload ID="FileDown" runat="server" />
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <span class="label label-default">Pasta Destino:</span>
                            <asp:FileUpload ID="FileDesti" runat="server" />
                        </td>
                    </tr>
                    <tr>
                        <th scope="row"></th>
                        <td>
                            <a data-toggle="modal" href="#ModalConfirm" class="btn-primary btn-block">SOLICITAR ENTREGA</a>
                        </td>
                    </tr>
                </tbody>
            </table>
        </form>
        <div id="ModalConfirm" class="modal fade in">
            <div class="modal-dialog">
                <div class="modal-content">
                    <div class="modal-header">
                    </div>
                    <div class="modal-body">
                        <p>Solicitar  entrega automática?</p>
                    </div>
                    <div class="modal-footer">
                        <div class="btn-group">
                            <button class="btn-danger btn-xs" data-dismiss="modal"><span class="glyphicon glyphicon-remove"></span>Não</button>
                            <button type="submit" id="btn1" class="btn-primary btn-group-lg" onserverclick="btn_Delivery" runat="server"><span class="glyphicon glyphicon-check"></span>Sim</button>
                        </div>
                    </div>
                </div>
            </div>
        </div>
        <p></p>
        <%--<a data-toggle="modal" href="#ModalConfirm" class="btn-primary btn-group-sm">SOLICITAR ENTREGA</a>--%>
    </div>
    <div class="col-md-5">
    </div>
</body>
</html>
</asp:Content>
is my codebehind has only pageload changes
  protected void Page_Load(object sender, EventArgs e)
    {
        //Obtendo cod cliente automatico           
            if (DropLabs.SelectedItem.Text.ToString() == "---")
            {
                codcli.Text = "";
            }
            else
            {
                codcli.Text = DropLabs.SelectedValue.ToString();//.Replace("0", "");
            }
    }
						
I had this problem too. In my case it was because there were two "Forms" on my masterpage. I was using a template and I forgot to remove "Form" from the template. I removed and solved my problem.
– Joao Ricardo Meira Lubas
I believe they already have, but this happens to me when there is a form tag on a page that uses a master page.
– Henrique