Sunday, August 26, 2012

ICALL BACK EVENT HANDLER

We have to play with 4 functions,

Two client side functions i.e. java script function, 
JavaScript Functions
RaiseCallbackEvent function gets call automatically whenever there is a CallbackEvent. And after this function 2nd function i.e. GetCallbackResult get called automatically.
DataBase Design
<html xmlns="http://www.w3.org/1999/xhtml">
    function ReceiveServerData(retValue) {
using System.Data.SqlClient;
public partial class AddPage : System.Web.UI.Page,ICallbackEventHandler
    }
    public void RaiseCallbackEvent(String eventArgument)
Output


Two server side function i.e. c# (in this case).

1 function ReceiveServerData(retValue)
2 function Checkusername 


.cs functions
1  public void RaiseCallbackEvent(String eventArgument)
 public String GetCallbackResult()





AddPage.aspx

<head runat="server">
    <title></title>
    <script type="text/javascript" language="javascript">
    function Checkusername ()
    {
        var values = document.getElementById("txtEname").value;
        CallServer(values, "");
    }

        if (retValue == "N") {
            alert("Please select another name; empname already exists");
            document.getElementById("txtEname").value = "";
            document.getElementById("txtEname").focus();
        }
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <table>
    <tr>
    <td>
        <asp:Label ID="Label1" runat="server" Text="Eno"></asp:Label>
    </td>
    <td>
        <asp:TextBox ID="txtEno" runat="server"  ></asp:TextBox>
    </td>
    </tr>
        <tr>
    <td>
        <asp:Label ID="Label2" runat="server" Text="Ename"></asp:Label>
    </td>
    <td>
        <asp:TextBox ID="txtEname" runat="server" onblur="javascript:Checkusername()"></asp:TextBox>
    </td>
    </tr>
    <tr>
    <td>
     <asp:Label ID="Label3" runat="server" Text="Designation"></asp:Label>
    </td>
    <td>
     <asp:TextBox ID="txtDesignation" runat="server"></asp:TextBox>
    </td>
    </tr>
    <tr>
    <td colspan="2" align="center">
        <asp:Button ID="btnSave" runat="server" Text="Save" onclick="btnSave_Click" />
    </td>
    </tr>
    </table>
    </div>
    </form>
</body>
</html>




AddPage.aspx.cs

using System.Configuration;

{
    protected String returnValue;
    protected void Page_Load(object sender, EventArgs e)
    {
        String cbReference = Page.ClientScript.GetCallbackEventReference(this, "arg","ReceiveServerData", "context");
        string callbackScript = "function CallServer(arg,context)" + "{" + cbReference + ";}";
        Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "CallServer", callbackScript,true);
    }
    protected void btnSave_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("user id=sa;password=uday;database=uday;data source=localhost");
        con.Open();
        SqlCommand cmd = new SqlCommand("insert into employee values(" + txtEno.Text + ",'" + txtEname.Text + "','" + txtDesignation.Text + "')", con);
        int i=cmd.ExecuteNonQuery();
        if(i>0)
        {
            Response.Redirect("Default.aspx");
        }
        con.Close();


    {
        SqlConnection con = new SqlConnection("user id=sa;password=uday;database=uday;data source=localhost");
        SqlCommand com = new SqlCommand("select *from employee where ename='" +eventArgument + "'", con);
        con.Open();
        SqlDataReader dr;
        dr = com.ExecuteReader();
        if (dr.HasRows == true)
        {
            returnValue = "N";
        }
        else
        {
            returnValue = "Y";
        }
        con.Close();
    }
    public String GetCallbackResult()
    {
        return returnValue;
    }
}




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