The Problem:

The user entered value is missing in the .Text attribute of the AjaxControlToolkit ComboBox when the enter key pressed. Also the “on change” events events are not called but I am not using postbacks anyway so I do not care.

Example:

private void BuildFileListDetails(NHibernateDataProvider _providerM)  
{  
    int resultsPage = Convert.ToInt32(ddlNavPageNumber.Text);  
    const int RESULTS_PAGE_SIZE = 100;  

    // The cbFileName.Text equals "" Not what user entered  
    string searchFileName= cbFileName.Text;  

    var xrfFiles = _providerM.GetXrfFiles(searchFileName, resultsPage, RESULTS_PAGE_SIZE);

    gvXrfFileList.DataSource = xrfFiles;

    gvXrfFileList.DataBind();

}

My Solution:

I needed to access the AjaxToolkit "ComboBox" imbedded TextBox control's .Text to access the value entered by user.

private void BuildFileListDetails(NHibernateDataProvider _providerM)
{

    int resultsPage = Convert.ToInt32(ddlNavPageNumber.Text); 
    const int RESULTS_PAGE_SIZE = 100;
    string searchFileName;

    //The Solution: Access the AjaxToolkit "ComboBox" imbedded TextBox control's .Text to access the value entered by user.
    TextBox textBox = cbFileName.FindControl("TextBox") as TextBox;
    if (textBox != null)
    {
       searchFileName = textBox.Text; //textBox.Text = "User Entered Value"
    }

    else
    {
       searchFileName = cbFileName.Text; 
    }

    var xrfFiles = _providerM.GetXrfFiles(searchFileName, resultsPage, RESULTS_PAGE_SIZE);
    gvXrfFileList.DataSource = xrfFiles;
    gvXrfFileList.DataBind();
}