방법: StructuralType 결과를 반환하는 쿼리 실행
이 항목에서는 EntityCommand 개체를 사용하여 개념적 모델에 대해 명령을 실행하는 방법과 StructuralType를 사용하여 EntityDataReader 결과를 검색하는 방법을 보여 줍니다. EntityType, RowType 및 ComplexType 클래스는 StructuralType 클래스에서 파생됩니다.
이 예제의 코드를 실행하려면
프로젝트에 AdventureWorks Sales 모델을 추가하고 Entity Framework를 사용하도록 프로젝트를 구성합니다. 자세한 내용은 방법: 엔터티 데이터 모델 마법사 사용을 참조하세요.
애플리케이션의 코드 페이지에서 Visual Basic에서 다음
using
지시문을 추가합니다Imports
.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 System.Data.Metadata.Edm;
Imports System.Collections.Generic Imports System.Collections Imports System.Data.Common Imports System.Data Imports System.IO Imports System.Data.SqlClient Imports System.Data.EntityClient Imports System.Data.Metadata.Edm
예시
이 예제에서는 EntityType 결과를 반환하는 쿼리를 실행합니다. 다음 쿼리를 ExecuteStructuralTypeQuery
함수에 인수로 전달하면 이 함수는 Products
에 대한 정보를 표시합니다.
SELECT VALUE Product FROM AdventureWorksEntities.Products AS Product
다음과 같은 매개 변수가 있는 쿼리를 전달하는 경우 EntityParameter 개체를 Parameters 개체의 EntityCommand 속성에 추가합니다.
SELECT VALUE product FROM AdventureWorksEntities.Products
AS product where product.ListPrice >= @price
static void ExecuteStructuralTypeQuery(string esqlQuery)
{
if (esqlQuery.Length == 0)
{
Console.WriteLine("The query string is empty.");
return;
}
using (EntityConnection conn =
new EntityConnection("name=AdventureWorksEntities"))
{
conn.Open();
// 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())
{
StructuralTypeVisitRecord(rdr as IExtendedDataRecord);
}
}
}
conn.Close();
}
}
static void StructuralTypeVisitRecord(IExtendedDataRecord record)
{
int fieldCount = record.DataRecordInfo.FieldMetadata.Count;
for (int fieldIndex = 0; fieldIndex < fieldCount; fieldIndex++)
{
Console.Write(record.GetName(fieldIndex) + ": ");
// 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;
// The EntityType, ComplexType and RowType are structural types
// that have members.
// Read only the PrimitiveType members of this structural type.
if (fieldTypeKind == BuiltInTypeKind.PrimitiveType)
{
// Primitive types are surfaced as plain objects.
Console.WriteLine(record.GetValue(fieldIndex).ToString());
}
}
}
}
Private Shared Sub ExecuteStructuralTypeQuery(ByVal esqlQuery As String)
If esqlQuery.Length = 0 Then
Console.WriteLine("The query string is empty.")
Exit Sub
End If
Using conn As New EntityConnection("name=AdventureWorksEntities")
conn.Open()
' Create an EntityCommand.
Using cmd As EntityCommand = conn.CreateCommand()
cmd.CommandText = esqlQuery
' Execute the command.
Using rdr As EntityDataReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess)
' Start reading results.
While rdr.Read()
StructuralTypeVisitRecord(TryCast(rdr, IExtendedDataRecord))
End While
End Using
End Using
conn.Close()
End Using
End Sub
Private Shared Sub StructuralTypeVisitRecord(ByVal record As IExtendedDataRecord)
Dim fieldCount As Integer = record.DataRecordInfo.FieldMetadata.Count
For fieldIndex As Integer = 0 To fieldCount - 1
Console.Write(record.GetName(fieldIndex) & ": ")
' 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
' The EntityType, ComplexType and RowType are structural types
' that have members.
' Read only the PrimitiveType members of this structural type.
If fieldTypeKind = BuiltInTypeKind.PrimitiveType Then
' Primitive types are surfaced as plain objects.
Console.WriteLine(record.GetValue(fieldIndex).ToString())
End If
End If
Next
End Sub