Sharepoint Infopath表单2013更改事件未更新表单中的值

我有一个infopath表单。在将事件更改为字段时，我正在更新另一个名为Shift的字段的值。为此，我编写了以下代码

public void To_Changed(object sender, XmlEventArgs e)
    {
        // Write your code here to change the main data source.
        ///my:myFields/my:RequestDetails/my:IndividualRequest/my:To
        // Write your code here.
        // Write your code here to change the main data source.
        ///my:myFields/my:RequestDetails/my:IndividualRequest/my:To
        try
        {
            XPathNavigator xmlDoc = this.MainDataSource.CreateNavigator();
            XPathNavigator xTo = xmlDoc.SelectSingleNode("my:myFields/my:RequestDetails/my:IndividualRequest/my:To", this.NamespaceManager);
            XPathNavigator xShift = xmlDoc.SelectSingleNode("/my:myFields/my:RequestDetails/my:IndividualRequest/my:Shifts", this.NamespaceManager);



            xShift.SetValue("6");

        }
        catch (Exception ex)
        {
            Log.WriteLog(ex);

        }
    }  

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我已经发布了表单，并将表单作为contenttype上传。但是，当我在infpath表单中更改To值时，Shift字段值不会更新。

我已使用infopath中的规则解决了此问题