加载xml字符串报错 “Illegal characters in path.”

有一个字符串 xmlEntitySetting 里面存的是下面xml格式的字符
<entities>
<entity EntityType="Zesing.Common.Entities.EntityPropertySetting, Zesing.Framework.Common, Version=1.1.0.0, Culture=neutral, PublicKeyToken=null">
<KnownTypes>
  <KnownType>Zesing.Common.Entities.EntityPropertySetting, Zesing.Framework.Common, Version=1.1.0.0, Culture=neutral, PublicKeyToken=null</KnownType> 
  </KnownTypes>
 <EntityPropertySetting xmlns="http://schemas.datacontract.org/2004/07/Zesing.Common.Entities" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <AllowNull>true</AllowNull> 
  <Description /> 
  <EditorKind>Text</EditorKind> 
  <FieldName>Id</FieldName> 
  <Hint /> 
  <Index>0</Index> 
  <IsInternalEditor>true</IsInternalEditor> 
  <IsPrimaryKey>false</IsPrimaryKey> 
  <IsPyWbField>false</IsPyWbField> 
  <PasswordSupport>false</PasswordSupport> 
 <PropertyEditor>
  <DataSource>qqq</DataSource> 
  <DataSourceKey>qqq</DataSourceKey> 
  <DataSourceKind>qqq</DataSourceKind> 
  <DataSourceName>qqq</DataSourceName> 
  <EditorKind>qqq</EditorKind> 
  <Enable>true</Enable> 
  <FilterByPyWb>true</FilterByPyWb> 
  <KeyCaption>qqq</KeyCaption> 
  <NameCaption>qqq</NameCaption> 
  </PropertyEditor>
  <ReadOnly>false</ReadOnly> 
  <RealValueType>varchar</RealValueType> 
  <Visible>true</Visible> 
  </EntityPropertySetting>
  </entity>
  </entities>用 XmlDocument docEntity = new XmlDocument();
      docEntity.Load(xmlEntitySetting);
方法加载时报错Illegal characters in path.在线坐等