vb.net - 我可以覆盖 SqlCommand 函数吗？

Question

我有例如代码

Dim cmd As New SqlClient.SqlCommand(commandString, databaseString) 
Dim result As Integer

Try
    result = cmd.ExecuteScalar()
Catch e as Exception
    'catch exception code
End Try

除了这样做，我可以覆盖 ExecuteScalar 函数来进行某种通用异常捕获吗？

Answer 1

您还可以使用组合：

Public Class SqlCommandManager
Private _sqlCommand As System.Data.SqlClient.SqlCommand
Public Sub New(command As System.Data.SqlClient.SqlCommand)

    If command Is Nothing Then
        Throw New ArgumentNullException("command")
    End If

    _sqlCommand = command
End Sub
Private ReadOnly Property Command As System.Data.SqlClient.SqlCommand
    Get
        Return _sqlCommand
    End Get
End Property
Public Function ExecuteScalar() As Object
    Dim result As Object

    Try
        result = Command.ExecuteScalar()
    Catch e As Exception
        'catch exception code
    End Try

    Return result
End Function
End Class

不是说这是最好的选择，只是说它是一个....

Answer 2

不，但您可以创建一个通用的DoExecuteScalar辅助函数，该函数采用 SQL 字符串和连接字符串：

Public Function DoExecuteScalar(commandString as String, databaseString as String) as Object
    Dim cmd as New SqlClient.SqlCommand(commandString, databaseString)
    Dim result as Integer
    Try
        result = cmd.ExecuteScalar()
    Catch e As Exception
        Return 0
    End Try
    Return result
End Function

Answer 3

不，您不能覆盖方法，因为您不能从它继承，因为SqlCommandis sealed。

在您使用的地方捕获（或抛出）异常有什么问题SqlCommand？