对Textbox onblur事件执行数据库查询

Question

I am using asp.net 3.5 with C#. I need to do a database lookup when a user enters ProductID in txtProductID. I guess doing javascript is out of the question since this will have to be server side call. I wrote this code in the page_load event of the webpage:

        protected void Page_Load(object sender, EventArgs e)
    {
        txtProductID.Attributes.Add("onblur", "LookupProduct()");
    }

        protected void LookupProduct()
    {
        //Lookup Product information on onBlur event;
    }

I get an error message: Microsoft JScript runtime error: Object expected How can I resolve this ?

Answer 1

onblur is a client-side event. LookupProduct is a server-side method. You can't reference one from the other - there's simply no association whatsoever between the two.

There's no quick fix for this - you have to either trigger a postback on the client event (using ClientScriptManager.GetPostBackEventReference ) or implement an Ajax callback using a library like Microsoft ASP.NET Ajax .

Alternatively, if you don't really need to fire this event on every blur, and only when the text has changed , then you can simply use the server-side TextBox.OnChanged event and set the TextBox's AutoPostBack property to true . Make sure you remember to set AutoPostBack , otherwise this won't get you anywhere.

Answer 2

Use the TextBox.TextChanged event.

ASPX markup:

<asp:TextBox ID="txtProductID" runat="server" AutoPostBack="true" OnTextChanged="txtProductID_TextChanged" />

Codebehind:

protected void txtProductID_TextChanged(object sender, EventArgs e)
{
   // do your database query here
}

Answer 3

This should do the trick, as referenced here: http://www.codedigest.com/CodeDigest/80-Calling-a-Serverside-Method-from-JavaScript-in-ASP-Net-AJAX---PageMethods.aspx

These are the controls

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="True" />
<asp:TextBox ID="txtTest" onblur="LookupProduct()" runat="server" />

This is the Javascript

<script language="javascript">
function LookupProduct()
{  
    PageMethods.LookupProduct('',OnSuccess, OnFailure);
}

function OnSuccess(result) {
    if (result)
    {
    }
}

function OnFailure(error) {
}
</script>

This is the server sidewebmethod

[WebMethod]
public static bool LookupProduct()
{
    return true;
}