使用Dapper从数据库中检索XML

Question

我正在使用Dapper查询包含XML字段的表:

CREATE TABLE Workflow
(
    Guid uniqueidentifier not null,
    State xml not null
)

然后将其映射到XDocument类型的属性:

public class Workflow
{
    public Guid InstanceId { get;set; }
    public XDocument State { get;set; }
}

但是当我尝试查询表时,我收到以下错误:

Error parsing column 1 (State= - String)
   at Dapper.SqlMapper.ThrowDataException(Exception ex, Int32 index, IDataReader reader, Object value) in d:\\Dev\\dapper-dot-net\\Dapper NET40\\SqlMapper.cs:line 4045
   at Deserialize038b29f4-d97d-4b62-b45b-786bd7d50e7a(IDataReader )
   at Dapper.SqlMapper.<QueryImpl>d__11`1.MoveNext() in d:\\Dev\\dapper-dot-net\\Dapper NET40\\SqlMapper.cs:line 1572
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in d:\\Dev\\dapper-dot-net\\Dapper NET40\\SqlMapper.cs:line 1443
   at MyProject.DapperBase.Query[TResult](String command, DynamicParameters parameters, IDbTransaction transaction, Boolean buffered, Int32 commandTimeout) in d:\\MyProject\\DapperBase.cs:line 122
   at MyProject.WorkflowData.Get(Guid identifier) in d:\\MyProject\\WorkflowData.cs:line 41
   at MyProject.WorkflowLogic.Save(Workflow workflow) in d:\\MyProject\\WorkflowLogic.cs:line 34
   at MyProject.WorkflowsController.Save(Guid id, WorkflowRequest request) in d:\\MyProject\\WorkflowsController.cs:line 97

InnerException: Invalid cast from 'System.String' to 'System.Xml.Linq.XDocument'.
    at System.Convert.DefaultToType(IConvertible value, Type targetType, IFormatProvider provider)at System.String.System.IConvertible.ToType(Type type, IFormatProvider provider)
    at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
    at System.Convert.ChangeType(Object value, Type conversionType)
    at Deserialize038b29f4-d97d-4b62-b45b-786bd7d50e7a(IDataReader )

除了修改我的POCO以使用字符串数据类型然后将字符串转换为其他地方的XDocument之外,有没有办法让Dapper正确地从数据库中反序列化XML？

Answer 1

最后，我只是暴力破解：

public class Workflow
{
    public Guid InstanceId { get;set; }
    public XDocument StateIn { set { State = value.ToString(); } }
    public string State { get;set; }
    public XDocument StateOut { get { return XDocument.Parse(State); } }
}

Dapper 处理 State 值，我只是在 StateIn 上设置该值并从 StateOut 读取它。我觉得提出这样的解决方案有点肮脏，但是嘿，它有效。