dapper 自定义数据库字段和代码中Model字段不一致时候的mapping方法

namespace YourNamespace
{
    /// <summary>
    /// Uses the Name value of the ColumnAttribute specified, otherwise maps as usual.
    /// </summary>
    /// <typeparam name="T">The type of the object that this mapper applies to.</typeparam>
    public class ColumnAttributeTypeMapper<T> : FallbackTypeMapper
    {
        public ColumnAttributeTypeMapper()
            : base(new SqlMapper.ITypeMap[]
                {
                    new CustomPropertyTypeMap(
                       typeof(T),
                       (type, columnName) =>
                           type.GetProperties().FirstOrDefault(prop =>
                               prop.GetCustomAttributes(false)
                                   .OfType<ColumnMappingAttribute>()
                                   .Any(attr => attr.Name == columnName)
                               )
                       ),
                    new DefaultTypeMap(typeof(T))
                })
        {
        }
    }
    
  [AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
    public class ColumnMappingAttribute : Attribute
    {
        public string Name { get; set; }
    }
 
  public class FallbackTypeMapper : SqlMapper.ITypeMap
    {
        private readonly IEnumerable<SqlMapper.ITypeMap> _mappers;
 
        public FallbackTypeMapper(IEnumerable<SqlMapper.ITypeMap> mappers)
        {
            _mappers = mappers;
        }
 
 
        public ConstructorInfo FindConstructor(string[] names, Type[] types)
        {
            foreach (var mapper in _mappers)
            {
                try
                {
                    ConstructorInfo result = mapper.FindConstructor(names, types);
                    if (result != null)
                    {
                        return result;
                    }
                }
                catch (NotImplementedException)
                {
                }
            }
            return null;
        }
 
        public SqlMapper.IMemberMap GetConstructorParameter(ConstructorInfo constructor, string columnName)
        {
            foreach (var mapper in _mappers)
            {
                try
                {
                    var result = mapper.GetConstructorParameter(constructor, columnName);
                    if (result != null)
                    {
                        return result;
                    }
                }
                catch (NotImplementedException)
                {
                }
            }
            return null;
        }
 
        public SqlMapper.IMemberMap GetMember(string columnName)
        {
            foreach (var mapper in _mappers)
            {
                try
                {
                    var result = mapper.GetMember(columnName);
                    if (result != null)
                    {
                        return result;
                    }
                }
                catch (NotImplementedException)
                {
                }
            }
            return null;
        }
    }
  
}
public static IEnumerable LoadWithCustomMapping()
{
    using (var conn = OpenDBConnection())
    {
        Dapper.SqlMapper.SetTypeMap(typeof(MyArea), new ColumnAttributeTypeMapper());
        return conn.Query("SELECT TOP 10 CAID,CAName,En FROM CityArea");
    }
}

 

posted @ 2014-10-20 23:14  不能失败  阅读(7229)  评论(2编辑  收藏  举报