VB.Net/Database ADO.net/Scalar Data

Материал из VB Эксперт
Версия от 15:44, 26 мая 2010; Admin (обсуждение | вклад) (1 версия)
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Execute Row Count: Scalar data

<source lang="vbnet"> Imports System Imports System.Collections Imports System.Data Imports System.IO Imports System.Xml.Serialization Imports System.Xml Imports System.Windows.Forms Imports System.Data.SqlClient

Public Class MainClass

   Shared Dim WithEvents con As SqlConnection
   Shared Sub Main()
       con = New SqlConnection("Server=(local)\SQLEXPRESS;Initial Catalog=MyDatabase;Integrated Security=SSPI") 
       Dim cmd As New SqlCommand()
       cmd.rumandText = "SELECT COUNT(*) FROM Employee"
       cmd.Connection = con
       Try
           con.Open()
           Console.WriteLine("{0} - {1}", _
                           "cmd.ExecuteScalar()", cmd.ExecuteScalar().ToString())
       Finally
           con.Close()
       End Try
   End Sub

End Class

      </source>


ExecuteScalar: select count(*) from your table

<source lang="vbnet"> Imports System Imports System.Data Imports System.Data.SqlClient public class MainClass

  Shared Sub Main()
     Dim thisConnection As New SqlConnection("server=(local)\SQLEXPRESS;" & _
         "integrated security=sspi;database=MyDatabase")
     "Create Command object
     Dim nonqueryCommand As SqlCommand = thisConnection.CreateCommand()
     Try
        " Open Connection
        thisConnection.Open()
        Console.WriteLine("Connection Opened")
        "Create Command objects
        Dim scalarCommand As New SqlCommand("SELECT COUNT(*) FROM Employee", thisConnection)
        " Execute Scalar Query
        Console.WriteLine("Before INSERT, Number of Employees = {0}", _
           scalarCommand.ExecuteScalar())
     Catch ex As SqlException
        " Display error
        Console.WriteLine("Error: " & ex.ToString())
     Finally
        " Close Connection
        thisConnection.Close()
        Console.WriteLine("Connection Closed")
     End Try
  End Sub

End Class

      </source>


Mulitple results: Get result set from two "select" command

<source lang="vbnet"> Imports System Imports System.Collections Imports System.Data Imports System.IO Imports System.Xml.Serialization Imports System.Xml Imports System.Windows.Forms Imports System.Data.SqlClient

Public Class MainClass

   Shared Dim WithEvents con As SqlConnection
   Shared Sub Main()
       con = New SqlConnection("Server=(local)\SQLEXPRESS;Initial Catalog=MyDatabase;Integrated Security=SSPI") 
       Dim cmd As New SqlCommand()
       cmd.rumandText = "SELECT * FROM Employee; SELECT * FROM Employee"
       cmd.Connection = con
       Try
           con.Open()
           Dim reader As SqlDataReader = cmd.ExecuteReader()
           Do
               While reader.Read()
                   Console.WriteLine(reader(0) & vbTab & reader(1))
               End While
           Loop While reader.NextResult()
           reader.Close()
       Finally
           con.Close()
       End Try
   End Sub

End Class

      </source>