RelationalStorage.ReadAsync<TResult> 方法

定義

命名空間:

Orleans.SqlUtils

組件:

OrleansSQLUtils.dll

套件:

Microsoft.Orleans.OrleansSqlUtils v1.5.10

執行指定的 語句。 特別要搭配 SELECT 語句使用。

public System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<TResult>> ReadAsync<TResult> (string query, Action<System.Data.IDbCommand> parameterProvider, Func<System.Data.IDataRecord,int,System.Threading.CancellationToken,System.Threading.Tasks.Task<TResult>> selector, System.Threading.CancellationToken cancellationToken = default, System.Data.CommandBehavior commandBehavior = System.Data.CommandBehavior.Default);

abstract member ReadAsync : string * Action<System.Data.IDbCommand> * Func<System.Data.IDataRecord, int, System.Threading.CancellationToken, System.Threading.Tasks.Task<'Result>> * System.Threading.CancellationToken * System.Data.CommandBehavior -> System.Threading.Tasks.Task<seq<'Result>>
override this.ReadAsync : string * Action<System.Data.IDbCommand> * Func<System.Data.IDataRecord, int, System.Threading.CancellationToken, System.Threading.Tasks.Task<'Result>> * System.Threading.CancellationToken * System.Data.CommandBehavior -> System.Threading.Tasks.Task<seq<'Result>>

Public Function ReadAsync(Of TResult) (query As String, parameterProvider As Action(Of IDbCommand), selector As Func(Of IDataRecord, Integer, CancellationToken, Task(Of TResult)), Optional cancellationToken As CancellationToken = Nothing, Optional commandBehavior As CommandBehavior = System.Data.CommandBehavior.Default) As Task(Of IEnumerable(Of TResult))

類型參數

TResult

結果類型。

參數

query

String

執行指定的 語句。 特別要搭配 SELECT 語句使用。

parameterProvider

Action<IDbCommand>

將參數新增至查詢。 參數名稱必須符合查詢中定義的名稱。

selector

Func<IDataRecord,Int32,CancellationToken,Task<TResult>>

此函式會轉換原始 IDataRecord 結果，以輸入 Int32 做為結果集編號的參數。

cancellationToken

CancellationToken

取消語彙基元。 預設值為 None。

commandBehavior

CommandBehavior

應該使用的命令列為。 預設值為 Default。

傳回

Task<IEnumerable<TResult>>

物件清單，作為 的結果 。

實作

ReadAsync<TResult>(String, Action<IDbCommand>, Func<IDataRecord,Int32,CancellationToken,Task<TResult>>, CancellationToken, CommandBehavior)

範例

此範例示範如何進行手動調整的資料庫呼叫。

 //This struct holds the return value in this example.
 public struct Information
 {
     public string TABLE_CATALOG { get; set; }
     public string TABLE_NAME { get; set; }
 }

 //Here are defined two queries. There can be more than two queries, in which case
 //the result sets are differentiated by a count parameter. Here the queries are
 //SELECT clauses, but they can be whatever, even mixed ones.
 IEnumerable<Information> ret =
     await storage.ReadAsync<Information>("SELECT * FROM INFORMATION_SCHEMA.TABLES; SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = @tp1", command =>
 {
     //Parameters are added and created like this.
     //They are database vendor agnostic.
     var tp1 = command.CreateParameter();
     tp1.ParameterName = "tp1";
     tp1.Value = "some test value";
     tp1.DbType = DbType.String;
     tp1.Direction = ParameterDirection.Input;
     command.Parameters.Add(tp1);

     //The selector is used to select the results within the result set. In this case there are two homogenous
     //result sets, so there is actually no need to check which result set the selector holds and it could
     //marked with by convention by underscore (_).
 }, (selector, resultSetCount) =>
    {
        //This function is called once for each row returned, so the final result will be an
        //IEnumerable<Information>.
        return new Information
        {
            TABLE_CATALOG = selector.GetValueOrDefault<string>("TABLE_CATALOG"),
            TABLE_NAME = selector.GetValueOrDefault<string>("TABLE_NAME")
        }               
}).ConfigureAwait(continueOnCapturedContext: false);