I'm using ASP.NET AJAX 1.0 to validate and lookup a textbox value in a mmGridView edit line.

<edititemtemplate>
    <mm:mmTextBox id="txtMyValue" runat="server" Text='< %# Bind("myvalue") % >' 
        AutoPostBack="true" MaxLength="9" Width="76px" 
        OnTextChanged="txtMyValue_TextChanged">
    </mm:mmTextBox>
</edititemtemplate>

I'm running into a few problems:

When the textbox posts back this code code runs in Page_Load(), I retrieve the DataSet:

public partial class MyPage : mmBusinessWebPage
{
    protected MyBusiness oMyBusiness;
    protected DataSet dsMyBusiness;

    protected void Page_Load(object sender, EventArgs e)
    {
        this.oMyBusiness = (MyBusiness)this.RegisterPrimaryBizObj(new MyBusiness());

        if (!IsPostBack)
        {
            // Load Data
            this.oMyBusiness.GetData(key);
            Session["dsMyBusiness"] = this.oMyBusiness.DataSet;
        }
        else
        {
            // *** this code runs before the TextChanged method ***
            DataSet dsMyBusiness= (DataSet)Session["dsMyBusiness"];
            this.oMyBusiness.SetCurrentDataSet(dsMyBusiness);
            Session["dsMyBusiness"] = this.oMyBusiness.DataSet;
        }
    }
}

But in the TextChanged method the DataSet set in Page_Load() is Null. Why is that?

I'm also having the problems marked with "***". Any help appreciated. Thanks!

    /// <summary>
    /// AJAX postback!!! - Check MyValue and set description
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void txtMyValue_TextChanged(object sender, EventArgs e)
    {
        // *** Why is this.dsMyBusiness Null here? ****
        DataSet ds2 = this.dsMyBusiness;

        // workaround
        DataSet ds = (DataSet)Session["dsMyBusiness"];
        this.dsMyBusiness.SetCurrentDataSet(ds);

        // *** is this a mistake? ***
        // *** why doesn't this hydrate the row.DataItem below? ***
        // Rebind the GridView
        this.BindControl(this.gvMyGrid);
        // 

        mmTextBox tb = (mmTextBox)sender;

        // if the value exists get the description for the value
        string myvalue = tb.Text.Replace("-", String.Empty).Trim();
        MyForeignTableEntity ftEntity;
        ftEntity = oMyForeignTable.GetDescription(myvalue);

        // find the description controls
        GridViewRow row = this.gridCountSheet.Rows[this.gridCountSheet.EditIndex];

        mmLabel lblDescription = (mmLabel)row.Cells[COL_DESCRIPTION].FindControl("lblDescription");
        mmTextBox txtDescription = (mmTextBox)row.Cells[COL_DESCRIPTION].FindControl("txtDescription");

        // get the row data
        // *** Why is this Null? ***
        // Note: The DataItem property is only available during and after the RowDataBound event of a GridView control.
        // DataRowView drv = row.DataItem as DataRowView;
       
        // workaround - use dataset
        // ??? will EditIndex work when paging is implemented?
        DataRow dr = ds.Tables[0].Rows[this.gridCountSheet.EditIndex];

        // handle updates
        if (ftEntity == null || 
            ftEntity.Description == null || 
            ftEntity.Description == String.Empty)
        {
            // NOT found
            lblDescription.Visible = false;
            txtDescription.Visible = true;
            // put not found value in description text box
            txtDescription.Text = tb.Text;
            // clear not found value
            tb.Text = String.Empty;

            // store in data row
            dr["myvalue"] = String.Empty;
            dr["description"] = tb.Text;
        }
        else
        {
            // found
            lblDescription.Visible = true;
            txtDescription.Visible = false;
            lblDescription.Text = ftEntity.Description;
            txtDescription.Text = ftEntity.Description;

            dr["myvalue"] = myvalue;
            dr["description"] = ftEntity.Description;

        }
        // *** no other values from other controls are saved!!! ***
        // 1) set entire data row manually from controls?
        // 2) using wrong data/binding concept here?
        // 3) set flag here and handle this method's functionality in RowDataBound()? 
        // ********************************************
        
        // Store the DataSet back into the session
        Session["dsMyBusiness"] = ds;
        // Rebind the GridView
        this.BindControl(this.gvMyGrid);
    }