How to Clear all controls in web page

public void ClearControls(Control ctrl)
    {
        if (ctrl.Controls.Count > 0)
        {
            for (int i = 0; i < ctrl.Controls.Count; i++)
            {

                ClearControls(ctrl.Controls[i]);
            }
        }
        switch (ctrl.GetType().ToString())
        {
            case "System.Web.UI.WebControls.TextBox":
                TextBox txt = (TextBox)ctrl;
                txt.Text = null;
                break;
            case "System.Web.UI.WebControls.DropDownList":
                DropDownList ddl = (DropDownList)ctrl;
                ddl.SelectedIndex = 0;
                break;
        }
    }

    public void FillSelectAny(Control ctrl)
    {
        switch (ctrl.GetType().ToString())
        {          
            case "System.Web.UI.WebControls.DropDownList":
                DropDownList ddl = (DropDownList)ctrl;
                ddl.Items.Insert(0, "-- Select Any --");
                ddl.Items[0].Value = "0";
                break;
        }
    }

How to Add Products In to Cart

protected void addcart_Click(object sender, ImageClickEventArgs e)
    {
        if (ViewState["CurrentData"] != null)
        {
            DataTable dt = (DataTable)ViewState["CurrentData"];
            int count = dt.Rows.Count;
            BindGrid(count);

        }
        else
        {
            BindGrid(1);

        }
    }




private void BindGrid(int rowcount)
    {
        DataTable dt = new DataTable();
        DataRow dr;

        dt.Columns.Add(new System.Data.DataColumn("Cost", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("ProductName", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("ProductId", typeof(String)));


        if (ViewState["CurrentData"] != null)
        {
            for (int i = 0; i < rowcount + 1; i++)
            {
                dt = (DataTable)ViewState["CurrentData"];
                if (dt.Rows.Count > 0)
                {
                    dr = dt.NewRow();
                    dr[0] = dt.Rows[0][0].ToString();

                }
            }
            ds = obj.GetProductById(Convert.ToInt32(Session["DetailsId"].ToString()));
            dr = dt.NewRow();
            dr[0] = ds.Tables[0].Rows[0]["Cost"].ToString();
            dr[1] = ds.Tables[0].Rows[0]["ProductName"].ToString();
            dr[2] = ds.Tables[0].Rows[0]["ProductId"].ToString();
           

            dt.Rows.Add(dr);

        }
        else
        {
            ds = obj.GetProductById(Convert.ToInt32(Session["DetailsId"].ToString()));
            dr = dt.NewRow();
            dr[0] = ds.Tables[0].Rows[0]["Cost"].ToString();
            dr[1] = ds.Tables[0].Rows[0]["ProductName"].ToString();
            dr[2] = ds.Tables[0].Rows[0]["ProductId"].ToString();
           

            dt.Rows.Add(dr);

        }

        // If ViewState has a data then use the value as the DataSource
       
        // Store the DataTable in ViewState to retain the values
        ViewState["CurrentData"] = dt;
        Session["Cart"] = dt;
        string lbl = dt.Rows.Count.ToString();
        lblCart .Text = "Total Items In Cart(" + lbl + ")";



    }


Saving Cart details into database



DataTable dt = (DataTable)Session["Cart"];

                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    string productId = dt.Rows[i]["ProductId"].ToString();

                    string productname = dt.Rows[i]["ProductName"].ToString();
                    string cost = dt.Rows[i]["Cost"].ToString();
                   
                    obj.insertcart(Convert.ToInt32(productId), productname, cost);

                   


                }

How to handle large file uploads which exceeds the configured request length Say you have in web config :

Snippet

<httpRuntime maxRequestLength="4048" />

Cause:
When you try to upload a file grater then 4MB you will get an error with the status of 404.13. To catch this error we have to utilise Application_Error as .net framework does not generate a request object and initiate a page lifecycle for this type of request. So no events get fired, but first of all you will end up in a error page.
What we can do is:
In Global.asax file:

protected void Application_Error(object sender, EventArgs e)

{

    if (HttpContext.Current.Request.Url.ToString().Contains("FileUpload.aspx") && 

        HttpContext.Current.Error.InnerException.Message.Contains("Maximum request length exceeded"))

    {

        HttpContext.Current.ClearError();

        HttpContext.Current.Response.Redirect(

            string.Format("~/FileUpload.aspx?Message={0}", "Upload file is over the allowed limit"));

    }

}

Then you can FileUpload.aspx like this:

<html xmlns="http://www.w3.org/1999/xhtml">

<head id="Head1" runat="server">

    <script runat="server">

        protected override void OnLoad(EventArgs e)

        {

            base.OnLoad(e);

            string message = this.Request.QueryString.Get("Message");

            if (!string.IsNullOrEmpty(message)) this.lblMessage.Text = message;

            else this.lblMessage.Visible = false;

        }

        protected void Save(object sender, EventArgs e)

        {

            

        }

    </script>

</head>

<body>

    <form id="form1" runat="server">

    <div>

        <asp:Label runat="server" ID="lblMessage" />

        <asp:FileUpload runat="server" ID="fuFile" />

        <asp:Button runat="server" ID="btnSave" Text="Save" />

    </div>

    </form>

</body>

</html>

How to print ASCII charactors in asp.net

<%@ Page Language="C#" %>

<html xmlns="http://www.w3.org/1999/xhtml">

<head id="Head1" runat="server">

    <script runat="server">

        protected override void OnLoad(EventArgs e)

        {

            base.OnLoad(e);

            TableRow tr = new TableRow();

            int index = 0;

            for (int i = 31; i < 256; i++)

            {

                string text = string.Format("{0:000} - (&#{0})", i);

                if (index % 10 == 0)

                {

                    tr = new TableRow();

                    this.tblCharSet.Rows.Add(tr);

                }

                tr.Cells.Add(new TableCell() { Text = text });

                this.ddlCharactors.Items.Add(new ListItem(string.Format("{0:000}", i), i.ToString()));

                index++;

            }

        }     

    </script>

</head>

<body>

    <form id="form1" runat="server">

        <asp:DropDownList ID="ddlCharactors" runat="server" />

        <asp:Table runat="server" ID="tblCharSet" />

    </form>

</body>

</html>

How to stop a asp.net button being postback to server

Attach an OnClientClick java script function with return inline. From the function return false based on your logic

<%@ Page Language="C#" %>

<html>

<head id="Head1" runat="server">

    <script type="text/javascript">

        function Validate() {

            alert("Validate Controls");

            var isValid = false;

            if (isValid)

                document.forms[0].submit();

            return false;

        }

    </script>

</head>

<body>

    <form id="form1" runat="server">

        <asp:Button runat="server" ID="btnLogin" 

            OnClientClick="javascript:return Validate()" 

            Text="Login" />

    </form>

</body>

</html>