<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<NewCont>
  <BaseInfo>
    <Missionid>00000000000058824904</Missionid>
    <SubMissionid>1</SubMissionid>
    <ActivityId>0000001002</ActivityId>
    <Managecom>86440601</Managecom>
    <PrtSeq>8104401614213</PrtSeq>
    <ContNo>00000035725392</ContNo>
  </BaseInfo>
  <ContInfo>
    <LCCont>
      <ContNo>00000035725392</ContNo>
      <PolApplyDate>2012-06-22</PolApplyDate>
      <CvaliDate>2012-06-22</CvaliDate>
      <AgentCode>37054128</AgentCode>
      <AgentName>黄东生</AgentName>
    </LCCont>
  </ContInfo>
</NewCont>

 protected void Page_Load(object sender, EventArgs e)
    {
        var str = "Missionid=00000000000058824904;SubMissionid=1;ActivityId=0000001002;AgentCode=37054128;CvaliDate=2012-06-22;ContNo=00000035725392";

        var xml0 = @"<BaseInfo>
<Missionid>{0}</Missionid>
<SubMissionid>{1}</SubMissionid>
<ActivityId>{2}</ActivityId>
<Managecom>{3}</Managecom>
<PrtSeq>{4}</PrtSeq>
<ContNo>{5}</ContNo>
</BaseInfo>";
        var xml = string.Format(xml0, GetValue(str,"Missionid"), GetValue(str,"SubMissionid"), GetValue(str,"ActivityId"), GetValue(str,"Managecom"), GetValue(str,"PrtSeq"), GetValue(str,"ContNo"));

        TextBox1.Text = xml;
    }
    string GetValue(string inStr,string filedName)
    {
        var reg = filedName + "=([^;]+)";
        var m = Regex.Match(inStr, reg);
        return m.Success ? m.Groups[1].Value : "";
    }