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RefType 結果を返すクエリの実行方法 (EntityClient)

このトピックでは、EntityCommand を使用して Entity Data Model に対してコマンドを実行する方法と、EntityDataReader を使用して RefType 結果を取得する方法の例を示します。

この例のコードを実行するには

  1. AdventureWorks Sales Model をプロジェクトに追加し、Entity Framework を使用するようにプロジェクトを構成します。これを行うには、次のいずれかの操作を実行します。

  2. アプリケーションのコード ページで、次の using ステートメント (Visual Basic の場合は Imports) を追加します。

    Imports System
Imports System.Collections.Generic
Imports System.Collections
Imports System.Data.Common
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.EntityClient
Imports System.Data.Metadata.Edm
Imports System.IO
' Add AdventureWorksModel prepended with the root namespace for the project.
'Imports ProjectName.AdventureWorksModel

    using System;
using System.Collections.Generic;
using System.Collections;
using System.Data.Common;
using System.Data;
using System.IO;
using System.Data.SqlClient;
using System.Data.EntityClient;
using AdventureWorksModel;
using System.Data.Metadata.Edm;

例

コードをテストするには、次のクエリを引数として ExectueRefTypeQuery 関数に渡します。

"SELECT REF(p) FROM AdventureWorksEntities.Product as p"

上記のクエリは、RefType 結果を返します。

Sub ExectueRefTypeQuery(ByVal esqlQuery As String)
    If (esqlQuery.Length = 0) Then
        Console.WriteLine("The query string is empty.")
        Return
    End If

    Using conn As EntityConnection = New EntityConnection("name=AdventureWorksEntities")
        conn.Open()

        Try
            ' Create an EntityCommand.
            Using cmd As EntityCommand = conn.CreateCommand()
                cmd.CommandText = esqlQuery
                ' Execute the command.
                Using reader As EntityDataReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess)
                    Do While (reader.Read())
                        RefTypeVisitRecord(CType(reader, IExtendedDataRecord))
                    Loop
                End Using
            End Using
        Catch ex As Exception
            Console.WriteLine(ex.ToString())
        End Try
        conn.Close()
    End Using
End Sub

Sub RefTypeVisitRecord(ByVal record As IExtendedDataRecord)
    ' For RefType the record contains exactly one field.
    Dim fieldIndex As Integer
    fieldIndex = 0

    ' If the field is flagged as DbNull, the shape of the value is undetermined.
    ' An attempt to get such a value may trigger an exception.
    If (record.IsDBNull(fieldIndex) = False) Then
        Dim fieldTypeKind As BuiltInTypeKind = record.DataRecordInfo.FieldMetadata(fieldIndex).FieldType.TypeUsage.EdmType.BuiltInTypeKind()

        'read only fields that contain PrimitiveType
        If (fieldTypeKind = BuiltInTypeKind.RefType) Then
            ' Ref types are surfaced as EntityKey instances. 
            ' The containing record sees them as atomic.
            Dim key As EntityKey = CType(record.GetValue(fieldIndex), EntityKey)
            ' Get the EntitySet name.
            Console.WriteLine("EntitySetName " + key.EntitySetName)
            ' Get the Name and the Value information of the EntityKey.
            Dim keyMember As EntityKeyMember
            For Each keyMember In key.EntityKeyValues
                Console.WriteLine("   Key Name: " + keyMember.Key)
                Console.WriteLine("   Key Value: " + keyMember.Value)
            Next
        End If
    End If
End Sub

static void ExectueRefTypeQuery(string esqlQuery)
{
    if (esqlQuery.Length == 0)
    {
        Console.WriteLine("The query string is empty.");
        return;
    }

    using (EntityConnection conn =
        new EntityConnection("name=AdventureWorksEntities"))
    {
        conn.Open();

        try
        {
            // Create an EntityCommand.
            using (EntityCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = esqlQuery;
                // Execute the command.
                using (EntityDataReader rdr =
                    cmd.ExecuteReader(CommandBehavior.SequentialAccess))
                {
                    // Start reading results.
                    while (rdr.Read())
                    {
                        RefTypeVisitRecord(rdr as IExtendedDataRecord);
                    }
                }
            }
        }
        catch (EntityException ex)
        {
            Console.WriteLine(ex.ToString());
        }
        conn.Close();
    }
}

static void RefTypeVisitRecord(IExtendedDataRecord record)
{
    // For RefType the record contains exactly one field.
    int fieldIndex = 0;

    // If the field is flagged as DbNull, the shape of the value is undetermined.
    // An attempt to get such a value may trigger an exception.
    if (record.IsDBNull(fieldIndex) == false)
    {
        BuiltInTypeKind fieldTypeKind = record.DataRecordInfo.FieldMetadata[fieldIndex].
            FieldType.TypeUsage.EdmType.BuiltInTypeKind;
        //read only fields that contain PrimitiveType
        if (fieldTypeKind == BuiltInTypeKind.RefType)
        {
            // Ref types are surfaced as EntityKey instances. 
            // The containing record sees them as atomic.
            EntityKey key = record.GetValue(fieldIndex) as EntityKey;
            // Get the EntitySet name.
            Console.WriteLine("EntitySetName " + key.EntitySetName);
            // Get the Name and the Value information of the EntityKey.
            foreach (EntityKeyMember keyMember in key.EntityKeyValues)
            {
                Console.WriteLine("   Key Name: " + keyMember.Key);
                Console.WriteLine("   Key Value: " + keyMember.Value);
            }
        }
    }
}

参照

概念

Entity SQL リファレンス

その他のリソース

EntityClient の使用 (Entity Framework タスク)