Dapper 下划线
Dapper 下划线映射实体
- 解决方案
- 原理
- 测试
- 代码
- 测试结果
- 总结
解决方案
设置静态变量
DefaultTypeMap.MatchNamesWithUnderscores = true;
原理
dapper将字段映射实体，会先创建DufaultTypeMap，在该类中处理Sql查询字段映射逻辑：
- 先查找属性，完全匹配，如果没有匹配到则判断是否进行匹配下划线，最后判断是否存在属性，存在则返回实体成员属性映射关系类；
- 如果没有找到属性，就找字段，逻辑同上。
/// Mapping implementation
public SqlMapper.IMemberMap GetMember(string columnName)
{
//完全匹配
var property = Properties.Find(p => string.Equals(p.Name, columnName, StringComparison.Ordinal))
?? Properties.Find(p => string.Equals(p.Name, columnName, StringComparison.OrdinalIgnoreCase));
//判断是否需要进行下划线匹配
if (property == null && MatchNamesWithUnderscores)
{
property = Properties.Find(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.Ordinal))
?? Properties.Find(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.OrdinalIgnoreCase));
}
if (property != null)
return new SimpleMemberMap(columnName, property);
// ... 省略代码
}
/// 测试
代码
//带下划线
public class UserSimpleWithUnderscores
{
public string User_Id { get; set; }
public string User_Name { get; set; }
//测试全字段配置
public string Sex { get; set; }
}
//不带下划线
public class UserSimpleNotWithUnderscores
{
public string UserId { get; set; }
//重命名 不然会抛异常
//参考 https://blog.csdn.net/yiquan_yang/article/details/107341252
public string UName { get; set; }
public string Sex { get; set; }
}
//带下划线和不带 混合
public class UserSimpleMixtureAndRename
{
public string User_Id { get; set; }
public string UserName { get; set; }
public string ReSex { get; set; }
}
[Fact]
public void QueryUnderscores_Not_MatchNamesWithUnderscores()
{
var Id = "b4600fb2-61c3-4786-8ba1-9fc5387a8d17";
var userWith = _userRepository.QueryModel<UserSimpleWithUnderscores>("select user_id,user_name,sex from user where user_id=@Id", new { Id });
//相同查询参数会报错，这里user_name 改为 u_name
//参考 https://blog.csdn.net/yiquan_yang/article/details/107341252
//_userRepository是调用dapper不用管
var userNotWith = _userRepository.QueryModel<UserSimpleNotWithUnderscores>("select user_id,user_name u_name,sex from user where user_id=@Id", new { Id });
var userMix = _userRepository.QueryModel<UserSimpleMixtureAndRename>("select user_id,user_name,sex as resex from user where user_id=@Id", new { Id });
Assert.NotNull(userWith.User_Id);
Assert.NotNull(userWith.User_Name);
Assert.NotNull(userWith.Sex);
Assert.Null(userNotWith.UserId);
Assert.Null(userNotWith.UName);
Assert.NotNull(userNotWith.Sex);
Assert.NotNull(userMix.User_Id);
Assert.Null(userMix.UserName);
Assert.NotNull(userMix.ReSex);
}
[Fact]
public void QueryUnderscores_Has_MatchNamesWithUnderscores()
{
var Id = "b4600fb2-61c3-4786-8ba1-9fc5387a8d17";
DefaultTypeMap.MatchNamesWithUnderscores = true;
var userWith = _userRepository.QueryModel<UserSimpleWithUnderscores>("select user_id,user_name,sex from user where user_id=@Id", new { Id });
//相同查询参数会报错，这里user_name 改为 u_name
var userNotWith = _userRepository.QueryModel<UserSimpleNotWithUnderscores>("select user_id,user_name u_name,sex from user where user_id=@Id", new { Id });
var userMix = _userRepository.QueryModel<UserSimpleMixtureAndRename>("select user_id,user_name,sex as resex from user where user_id=@Id", new { Id });
Assert.NotNull(userWith.User_Id);
Assert.NotNull(userWith.User_Name);
Assert.NotNull(userWith.Sex);
Assert.NotNull(userNotWith.UserId);
Assert.NotNull(userNotWith.UName);
Assert.NotNull(userNotWith.Sex);
Assert.NotNull(userMix.User_Id);
Assert.NotNull(userMix.UserName);
Assert.NotNull(userMix.ReSex);
}
[Fact]
public void QueryUnderscores_NotThenHas_MatchNamesWithUnderscores()
{
var Id = "b4600fb2-61c3-4786-8ba1-9fc5387a8d17";
var userWith = _userRepository.QueryModel<UserSimpleWithUnderscores>("select user_id,user_name,sex from user where user_id=@Id", new { Id });
//相同查询参数会报错，这里user_name 改为 u_name
var userNotWith = _userRepository.QueryModel<UserSimpleNotWithUnderscores>("select user_id,user_name u_name,sex from user where user_id=@Id", new { Id });
var userMix = _userRepository.QueryModel<UserSimpleMixtureAndRename>("select user_id,user_name,sex as resex from user where user_id=@Id", new { Id });
Assert.NotNull(userWith.User_Id);
Assert.NotNull(userWith.User_Name);
Assert.NotNull(userWith.Sex);
Assert.Null(userNotWith.UserId);
Assert.Null(userNotWith.UName);
Assert.NotNull(userNotWith.Sex);
Assert.NotNull(userMix.User_Id);
Assert.Null(userMix.UserName);
Assert.NotNull(userMix.ReSex);
DefaultTypeMap.MatchNamesWithUnderscores = true;
userWith = _userRepository.QueryModel<UserSimpleWithUnderscores>("select user_id,user_name,sex from user where user_id=@Id", new { Id });
userNotWith = _userRepository.QueryModel<UserSimpleNotWithUnderscores>("select user_id,user_name u_name,sex from user where user_id=@Id", new { Id });
userMix = _userRepository.QueryModel<UserSimpleMixtureAndRename>("select user_id,user_name,sex as resex from user where user_id=@Id", new { Id });
Assert.NotNull(userWith.User_Id);
Assert.NotNull(userWith.User_Name);
Assert.NotNull(userWith.Sex);
Assert.Null(userNotWith.UserId);
Assert.Null(userNotWith.UName);
Assert.NotNull(userNotWith.Sex);
Assert.NotNull(userMix.User_Id);
Assert.Null(userMix.UserName);
Assert.NotNull(userMix.ReSex);
}
测试结果
总结
在Asp.Net Core中在Startup下加入
DefaultTypeMap.MatchNamesWithUnderscores = true;
注：千万不要动态在查询代码中配置，即要求有的查询需要兼容下划线，有的不允许兼容下划线，会非常难控制，参考测试代码第三个例子（将第一个第二个例子实体合并，查询结果是不一样的）。每个实体类进行了缓存
public static Func<Type, ITypeMap> TypeMapProvider = (Type type) => new DefaultTypeMap(type);
public static ITypeMap GetTypeMap(Type type)
{
if (type == null) throw new ArgumentNullException(nameof(type));
var map = (ITypeMap)_typeMaps[type];
if (map == null)
{
lock (_typeMaps)
{
map = (ITypeMap)_typeMaps[type];
if (map == null)
{
map = TypeMapProvider(type);
_typeMaps[type] = map;
}
}
}
return map;
}
// use Hashtable to get free lockless reading
private static readonly Hashtable _typeMaps = new Hashtable();
注：相似实体抛异常：Dapper Object must implement IConvertible.，相同查询字段不要声明多个实体。