/// <summary>
/// 执行查询，并返回单个对象
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryModel"></param>
/// <param name="returnDefaultWhenEmpty"></param>
/// <returns></returns>
public T ExecuteSingle <T>(QueryModel queryModel, bool returnDefaultWhenEmpty = true)
{
SqlServerQueryModelVisitor queryModelVisitor = new SqlServerQueryModelVisitor(_tblName);
var command = queryModelVisitor.Translate(queryModel);
using (IDataReader reader = this.provider.ExecuteQueryReader(command.ToString(), command.PrepareParameter().ToArray()))
{
bool isExists = reader.Read();
// 如果不存在查询记录
if (isExists == false)
{
// 如果可以默认
if (returnDefaultWhenEmpty)
{
return(default(T));
}
else
{
throw new InvalidOperationException("未查询出满足条件的任何记录。");
}
}
var tuple = reader.GetDeserializerState <T>();
return((T)tuple.Func(reader));
}
}
/// <summary>
/// 执行查询，并返回第一行第一列
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryModel"></param>
/// <returns></returns>
public T ExecuteScalar <T>(QueryModel queryModel)
{
var queryModelVisitor = new SqlServerQueryModelVisitor(_tblName);
var command = queryModelVisitor.Translate(queryModel);
return(provider.GetResult <T>(command.ToString(), command.PrepareParameter().ToArray()));
}
/// <summary>
/// 执行查询，并返回 IEnumerable<T> 对象
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryModel"></param>
/// <returns></returns>
public IEnumerable <T> ExecuteCollection <T>(QueryModel queryModel)
{
SqlServerQueryModelVisitor queryModelVisitor = new SqlServerQueryModelVisitor(_tblName);
var command = queryModelVisitor.Translate(queryModel);
using (IDataReader reader = this.provider.ExecuteQueryReader(command.ToString(), command.PrepareParameter().ToArray()))
{
using (reader)
{
var tuple = reader.GetDeserializerState <T>();
while (reader.Read())
{
yield return((T)tuple.Func(reader));
}
}
}
}
