vb.net 函数不会在所有代码路径上返回值。使用结果时可能会在运行时发生空引用异常
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Function doesn't return a value on all code paths. A null reference exception could occur at run time when the result is used
提问by HelpASisterOut
I'm getting this error:
我收到此错误：
Function 'getkey' doesn't return a value on all code paths. A null reference exception could occur at run time when the result is used.
函数“getkey”不会在所有代码路径上返回值。使用结果时，可能会在运行时发生空引用异常。
to the following code:
到以下代码：
Public Function getkey(ByVal id As String)
Dim cmd As SqlCommand
Try
cmd = New SqlCommand("dbo.getkeydesc", GenLog.cn)
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.AddWithValue("@id", id)
Dim r As SqlDataReader = cmd.ExecuteReader()
If r.HasRows Then
Return True
Else
Return False
End If
Catch ex As Exception
MsgBox(ex.ToString)
Finally
' If Not cn Is Nothing Then cn.Close()
End Try
End Function
I tried all possible solutions and they didn't work. Any help would be appreciated.
我尝试了所有可能的解决方案，但没有奏效。任何帮助，将不胜感激。
回答by Douglas Barbin
The Catchblock doesn't return a value. Change it to where it returns a value, like so:
该Catch块不返回值。将其更改为返回值的位置，如下所示：
Public Function getkey(ByVal id As String)
Dim cmd As SqlCommand
Try
cmd = New SqlCommand("dbo.getkeydesc", GenLog.cn)
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.AddWithValue("@id", id)
Dim r As SqlDataReader = cmd.ExecuteReader()
If r.HasRows Then
Return True
Else
Return False
End If
Catch ex As Exception
MsgBox(ex.ToString)
Return False
Finally
' If Not cn Is Nothing Then cn.Close()
End Try
End Function
回答by Bas
No value will be returned if an exception is thrown in that try..catch block. You either need to provide a return value in case an exception is thrown (by returning something in either the catch block, or you need to rethrow the exception.
如果在该 try..catch 块中抛出异常，则不会返回任何值。您要么需要提供一个返回值，以防抛出异常（通过在 catch 块中返回某些内容，或者您需要重新抛出异常。
Public Function getkey(ByVal id As String)
Dim cmd As SqlCommand
Try
cmd = New SqlCommand("dbo.getkeydesc", GenLog.cn)
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.AddWithValue("@id", id)
Dim r As SqlDataReader = cmd.ExecuteReader()
If r.HasRows Then
Return True
Else
Return False
End If
Catch ex As Exception
MsgBox(ex.ToString)
' Either do this:
' Return False
' or this:
' Throw ex
Finally
' If Not cn Is Nothing Then cn.Close()
End Try
End Function
