使用Dapper ORM检查记录是否存在

Question

使用Dapper ORM检查记录是否存在的最简单方法是什么？

我是否真的需要为查询定义POCO对象,我只想检查记录是否存在？

Answer 1

int id = ...
var exists = conn.ExecuteScalar<bool>("select count(1) from Table where Id=@id", new {id});

应该管用...

Answer 2

我认为这可能会减少一些开销，因为没有函数调用或数据类型转换：

int id = ...
var exists = connection.Query<object>(
    "SELECT 1 WHERE EXISTS (SELECT 1 FROM MyTable WHERE ID = @id)", new { id })
    .Any();

Answer 3

const string sql = "SELECT CAST(CASE WHEN EXISTS (SELECT 1 FROM MyTable WHERE Id = @Id) THEN 1 ELSE 0 END as BIT)";
bool exists = db.ExecuteScalar<bool>(sql, new { Id = 123 });