C#操作xmL文件

xml文件：

<?xml version="1.0" encoding="utf-8"?>
<AutoPrintProject>
  <Project>
    <ProjectName>SPA Reminder</ProjectName>
    <Status>Disable</Status>
    <LastPrintTime>2011-4-3 11:00:00</LastPrintTime>
    <Daily>1</Daily>
    <StartTime>2011/4/10 14:04:49</StartTime>
    <Printer>Microsoft XPS Document Writer</Printer>
    <SavePath>E:\IFCA\R2.8\PropertyNet\Bin</SavePath>
    <AllField>CompanyNo,ProjectName,Projectno,PhaseName,BlockName ,unitno
    </AllField>
    <letterid>51</letterid>
    <Operation>Equal,Greater,Not Equal,Like,Less</Operation>
    <WhereField>
      <Where>
        <WhereField>BlockName</WhereField>
        <WhereOperator>like</WhereOperator>
        <WhereValue>%陶%</WhereValue>
      </Where>
      <Where>
        <WhereField>unitno</WhereField>
        <WhereOperator>Equal</WhereOperator>
        <WhereValue>0010</WhereValue>
      </Where>
      <Where>
        <WhereField>CompanyNo</WhereField>
        <WhereOperator>Equal</WhereOperator>
        <WhereValue>10141</WhereValue>
      </Where>
      <Where>
        <WhereField>PhaseName</WhereField>
        <WhereOperator>Equal</WhereOperator>
        <WhereValue>422</WhereValue>
      </Where>
    </WhereField>
  </Project>
</AutoPrintProject>
 //读xml到table中
 public DataTable ReadXlm()
        {
            XmlDocument xmldoc = new XmlDocument();
            xmldoc.Load("AutoPrintProject.xml");
            XmlNode xn = xmldoc.SelectSingleNode("AutoPrintProject");
            XmlNodeList list = xn.ChildNodes;
            DataTable ta = new DataTable();
            ta.Columns.Add("JobName", typeof(string));
            ta.Columns.Add("Status", typeof(string));
            ta.Columns.Add("LastExecuteTime", typeof(string));
            foreach (XmlNode node in list)
            {
                XmlElement element = (XmlElement)node;
                DataRow row = ta.NewRow();
                row["JobName"] = element["ProjectName"].InnerText.ToString().Trim();
                row["Status"] = element["Status"].InnerText.ToString().Trim();
                row["LastExecuteTime"] = element["LastPrintTime"].InnerText.ToString().Trim();
                ta.Rows.Add(row);
            }
            return ta;
        }
//修改xml某个节点的值
 private void Start_Click(object sender, EventArgs e)
        {
             try
             {
                 string modifyvalue = dataGridView1.CurrentRow.Cells["JobName"].Value.ToString().Trim();
                 if (modifyvalue == "")
                 {
                     MessageBox.Show("请选择项目！");
                     return;
                 }
                 XmlDocument xmldoc = new XmlDocument();
                 xmldoc.Load("AutoPrintProject.xml");
                 XmlElement xn = (XmlElement)xmldoc.SelectSingleNode("AutoPrintProject/Project[ProjectName='" + modifyvalue + "']");
                 if (xn.GetElementsByTagName("Status").Item(0).InnerText != "Start")
                 {
                     xn.GetElementsByTagName("Status").Item(0).InnerText = "Start";
                     xmldoc.Save("AutoPrintProject.xml");
                     MessageBox.Show("工作启动成功！");
                 }
                 else
                 {
                     MessageBox.Show("该工作已经启动！");
                 }
                 refresh();
             }
             catch (Exception ex)
             {
                 MessageBox.Show("启动失败，原因：" + ex.Message.Trim());
             }
        }
//添加一个节点
 private void save_Click(object sender, EventArgs e)
        {
            try
            {
                if (ProjectName == "")
                {
                    MessageBox.Show("请选择项目！");
                    return;
                }
                string selectedfield=drop_field.SelectedValue.ToString().Trim();
                XmlDocument xmldoc = new XmlDocument();
                xmldoc.Load("AutoPrintProject.xml");
                XmlNode xn = xmldoc.SelectSingleNode("AutoPrintProject/Project[ProjectName='" + ProjectName + "']");
                if ((xn!=null)&&(!CheckField(selectedfield)))
                {
                    XmlNode xmlnode=(XmlNode)xn.SelectSingleNode("WhereField");

                    XmlElement xe1=xmldoc.CreateElement("Where");//创建一个节点

            
                    XmlNode subfieldwhere = xmldoc.CreateElement("WhereField");
                    subfieldwhere.InnerText = selectedfield;
                    xe1.AppendChild(subfieldwhere);

 

                    string selectedoperator = drop_operator.SelectedValue.ToString().Trim();
                    XmlNode suboperatorwhere = xmldoc.CreateElement("WhereOperator");
                    suboperatorwhere.InnerText = selectedoperator;
                    xe1.AppendChild(suboperatorwhere);

                    string selectedvalue = tb_value.Text.Trim();
                    XmlNode subvaluewhere = xmldoc.CreateElement("WhereValue");
                    subvaluewhere.InnerText = selectedvalue;
                    xe1.AppendChild(subvaluewhere);
                    xmlnode.AppendChild(xe1);

                    xmldoc.Save("AutoPrintProject.xml");
                    MessageBox.Show("增加字段成功！");

                    this.Close();
                    parent.Refresh();
                    //Criteria criteria = new Criteria();
                    //criteria.ProjectName = ProjectName;
                    //criteria.refresh();
                }
                else
                {
                    MessageBox.Show("该字段已经存在！");
                }

               
            }
            catch (Exception ex)
            {
                MessageBox.Show("增加字段失败，原因：" + ex.Message.Trim());
            }
        }
//删除一个节点
  private void DeleteField_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
        {
            MessageBoxButtons messButton = MessageBoxButtons.OKCancel;

            DialogResult dr = MessageBox.Show("确定删除吗?", "删除", messButton);

            try
            {
                if (dr == DialogResult.OK)//如果点击
                {
                    if (ProjectName == "")
                    {
                        MessageBox.Show("请选择项目！");
                        return;
                    }
                    string selectedfield = dataGridView1.CurrentRow.Cells["Field"].Value.ToString().Trim();
                    XmlDocument xmldoc = new XmlDocument();
                    xmldoc.Load("AutoPrintProject.xml");
                    XmlNode xn = xmldoc.SelectSingleNode("AutoPrintProject/Project[ProjectName='" + ProjectName + "']");
                    if (xn != null)
                    {
                        XmlNode xmlnode = (XmlNode)xn.SelectSingleNode("WhereField");

                        XmlNodeList nodelist = xmlnode.ChildNodes;
                        foreach (XmlNode one in nodelist)
                        {
                            XmlElement element = (XmlElement)one;
                            if (element.GetElementsByTagName("WhereField").Item(0).InnerText.Trim() == selectedfield)
                            {
                                xmlnode.RemoveChild(one);
                            }
                        }

                        xmldoc.Save("AutoPrintProject.xml");
                        MessageBox.Show("删除字段成功！");

                        refresh();
                    }
                    else
                    {
                        MessageBox.Show("删除字段失败！");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("删除字段失败，原因：" + ex.Message.Trim());
            }

        }