IRelationalStorage.ReadAsync<TResult> Method

Definition

Namespace:

Orleans.SqlUtils

Assembly:

OrleansSQLUtils.dll

Package:

Microsoft.Orleans.OrleansSqlUtils v1.5.10

Executes a given statement. Especially intended to use with SELECT statement.

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>>

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))

Type Parameters

TResult

The result type.

Parameters

query

String

The query to execute.

parameterProvider

Action<IDbCommand>

Adds parameters to the query. The parameters must be in the same order with same names as defined in the query.

selector

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

This function transforms the raw IDataRecord results to type <see paramref="TResult"></see> the Int32 parameter being the resultset number.

cancellationToken

CancellationToken

The cancellation token. Defaults to None.

commandBehavior

CommandBehavior

The command behavior that should be used. Defaults to Default.

Returns

Task<IEnumerable<TResult>>

A list of objects as a result of the <see paramref="query"></see>.

Examples

This sample shows how to make a hand-tuned database call.

 //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);