如何判断字符串是否为xml?

我们有一个字符串字段,可以包含XML或纯文本。XML不包含 <?xml

string redact(string eventDetail)
{
    string detail = eventDetail.Trim();
    if (!detail.StartsWith("<") && !detail.EndsWith(">")) return eventDetail;
    ...

XmlDocument.LoadXml XmlException

<TableName FirstField="Foo" SecondField="Bar" /> 
<TableName FirstField="Foo" SecondField="Bar" /> 
...

string redact(string eventDetail)
{
    if (string.IsNullOrEmpty(eventDetail)) return eventDetail; //+1 for unit tests :)
    string detail = eventDetail.Trim();
    if (!detail.StartsWith("<") && !detail.EndsWith(">")) return eventDetail;
    XmlDocument xml = new XmlDocument();
    try
    {
        xml.LoadXml(string.Format("<Root>{0}</Root>", detail));
    }
    catch (XmlException e)
    {
        log.WarnFormat("Data NOT redacted. Caught {0} loading eventDetail {1}", e.Message, eventDetail);
        return eventDetail;
    }
    ... // redact