SqlDataReader.IsDBNull(Int32) Methode

Definition

Namespace:
System.Data.SqlClient
Assembly:
System.Data.dll

Ruft einen Wert ab, der angibt, ob die Spalte nicht vorhandene oder fehlende Werte enthält.

public:
 virtual bool IsDBNull(int i);
public:
 override bool IsDBNull(int i);
public bool IsDBNull(int i);
public override bool IsDBNull(int i);
abstract member IsDBNull : int -> bool
override this.IsDBNull : int -> bool
override this.IsDBNull : int -> bool
Public Function IsDBNull (i As Integer) As Boolean
Public Overrides Function IsDBNull (i As Integer) As Boolean

Parameter

i
Int32

Die nullbasierte Spalten-Ordnungszahl.

Gibt zurück

Boolean

true ist der angegebene Spaltenwert gleichbedeutend mit DBNull; andernfalls false.

Implementiert

IsDBNull(Int32)

Hinweise

Rufen Sie diese Methode auf, um vor dem Aufrufen der eingegebenen Get-Methoden (z. B. , GetCharusw.) nach NULL-Spaltenwerten zu suchen, GetByteum das Auslösen eines Fehlers zu vermeiden.

using System;
using System.Data;
using System.Data.SqlClient;

class Program {
   static void Main(string[] args) {

      using (var connection = new SqlConnection(@"Data Source=(local);Initial Catalog=AdventureWorks2012;Integrated Security=SSPI")) {
         var command = new SqlCommand("SELECT p.FirstName, p.MiddleName, p.LastName FROM HumanResources.Employee AS e" +
                                 " JOIN Person.Person AS p ON e.BusinessEntityID = p.BusinessEntityID;", connection);
         connection.Open();
         var reader = command.ExecuteReader();
         while (reader.Read()) {
            Console.Write(reader.GetString(reader.GetOrdinal("FirstName")));
            // display middle name only of not null
            if (!reader.IsDBNull(reader.GetOrdinal("MiddleName")))
               Console.Write(" {0}", reader.GetString(reader.GetOrdinal("MiddleName")));
            Console.WriteLine(" {0}", reader.GetString(reader.GetOrdinal("LastName")));
         }
         connection.Close();
      }
   }
}

Imports System.Data
Imports System.Data.SqlClient

Module Module1
   Sub Main()
      Using connection As New SqlConnection("Data Source=(local);Initial Catalog=AdventureWorks2012;Integrated Security=SSPI")
         Dim command As New SqlCommand("SELECT p.FirstName, p.MiddleName, p.LastName FROM HumanResources.Employee AS e" & _
                                       " JOIN Person.Person AS p ON e.BusinessEntityID = p.BusinessEntityID;", connection)
         connection.Open()
         Dim reader As SqlDataReader = command.ExecuteReader()
         While reader.Read()
            Console.Write(reader.GetString(reader.GetOrdinal("FirstName")))

            ' display middle name only of not null
            If Not reader.IsDBNull(reader.GetOrdinal("MiddleName")) Then
               Console.Write(" {0}", reader.GetString(reader.GetOrdinal("MiddleName")))
            End If

            Console.WriteLine(" {0}", reader.GetString(reader.GetOrdinal("LastName")))
         End While
         connection.Close()
      End Using
   End Sub
End Module

Gilt für:

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