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[英]T must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'TModel' in the generic type or method
[英]Error: 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T'
我正在嘗試實現一個接受泛型T並返回T列表的方法。
public static List<T> GetMessages<T>(string query, int count, SqlConnection sqlconnection)
where T : ITable, new()
{
List<T> messages = new List<T>();
List<T> errorMessages = new List<T>();
DataSet response = DBUtils.ExecuteQueryScriptWithConnection(query, sqlconnection);
for (int i = 0; i < response.Tables[0].Rows.Count; ++i)
{
T message = new T();
DataRow row = response.Tables[0].Rows[i];
message.Id = Convert.ToInt32(row[0]);
message.CreatedDate = Convert.ToDateTime(row[1]);
}
return messages;
}
但是當我從另一個方法調用它時,我收到錯誤:
'T'必須是具有公共無參數構造函數的非抽象類型,才能在泛型類型或方法'
CIHelpers.TableHelpers.GetMessages<T>(string, int, System.Data.SqlClient.SqlConnection)
使用它作為參數'T'CIHelpers.TableHelpers.GetMessages<T>(string, int, System.Data.SqlClient.SqlConnection)
'
我稱之為的代碼:
List<T> messages = TableHelpers.GetMessages<T>(query, 1000, sqlconnection);
實現ITable的類(我傳遞的類型T就在這里。
public class MessageReceived : ITable
{
public int Id { get; set; }
public DateTime CreatedDate { get; set; }
string query = String.Format(@"select Id, CreatedDate, from MessageReceived where createddate > '2013-04-18 00:00:00.0000000'");
public MessageReceived()
{
}
}
我究竟做錯了什么?
調用代碼中的T
需要具有相同的約束。
否則,有人可以使用沒有構造函數的T
調用您的包裝函數。
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