public static IEnumerable <T> Query6 <T>(this IDbConnection cnn, string sql, object param = null) where T : new()
{
using (var command = cnn.CreateCommand())
{
command.CommandText = sql;
//dapper会在取缓存之前先正则匹配={变量名称}规格的替换
//Dapper Literal Replacements底层原理就是字串取代
CommandLiteralReplace(command, param);
using (var reader = command.ExecuteReader())
{
var identity = new DapperIdentity(command.CommandText, command.CommandType, cnn.ConnectionString, typeof(T), param?.GetType());
// 2. 如果cache有资料就使用,没有资料就动态建立方法并保存在缓存内
if (!readers.TryGetValue(identity, out Func <DbDataReader, object> func))
{
//动态建立方法
func = GetTypeDeserializerImpl(typeof(T), reader);
readers[identity] = func;
Console.WriteLine("没有缓存,建立动态方法放进缓存");
}
else
{
Console.WriteLine("使用缓存");
}
// 3. 呼叫生成的方法by reader,读取资料回传
while (reader.Read())
{
var result = func(reader as DbDataReader);
yield return(result is T ? (T)result : default(T));
}
}
}
}
public bool Equals(DapperIdentity other)
{
if (ReferenceEquals(this, other))
{
return(true);
}
if (ReferenceEquals(other, null))
{
return(false);
}
return(type == other.type &&
sql == other.sql &&
commandType == other.commandType &&
StringComparer.Ordinal.Equals(connectionString, other.connectionString) &&
parametersType == other.parametersType);
}
