vb.net上的这段代码给我这个错误:
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
知道为什么以及如何解决它吗？
Public Class Family
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
End Sub
Protected Sub saveButton_Click(sender As Object, e As EventArgs) Handles saveButton.Click
Dim clsFamily As New clsFamily
Session("Family") = clsFamily
If clsFamily Is Nothing Then
clsFamily = New clsFamily
Else
clsFamily = Session("Family")
End If
Dim eror As Integer = 0
Dim eror_message As String = "Wrong input, please try again"
If TBxPN.Text Is "" Or TBxPN.Text Is eror_message Or Regex.IsMatch(TBxPN.Text, "^[0-9 ]+$") Then
TBxPN.Text = eror_message
eror = 1
End If
If TBxOcc.Text Is "" Or TBxOcc.Text Is eror_message Or Regex.IsMatch(TBxOcc.Text, "^[0-9 ]+$") Then
TBxOcc.Text = eror_message
eror = 1
End If
If eror = 0 Then
For i = 0 To clsFamily.PersonName.Length
Dim newName As String
Dim newOccupation As String
Dim newDate As Date
Dim newGender As String
Dim newRelation As String
newName = TBxPN.Text
newOccupation = TBxOcc.Text
newDate = Calendar1.SelectedDate.ToShortDateString()
newGender = RBLGender.SelectedItem.Text
newRelation = CBLRelation.SelectedItem.Text
ReDim Preserve clsFamily.PersonName(i)
clsFamily.PersonName(i) = newName
ReDim Preserve clsFamily.Occupation(i)
clsFamily.Occupation(i) = newOccupation
ReDim Preserve clsFamily.DOB(i)
clsFamily.DOB(i) = newDate
ReDim Preserve clsFamily.Gender(i)
clsFamily.Gender(i) = newGender
ReDim Preserve clsFamily.RelationType(i)
clsFamily.RelationType(i) = newRelation
Next i
Session("Family") = clsFamily
End If
End Sub
Public Class clsFamily
Public PersonName() As String
Public RelationType() As String
Public DOB() As Date
Public Gender() As String
Public Occupation() As String
End Class
最佳答案
您的类中确实需要一个构造函数。下一个示例向personName数组添加一项:“”。这意味着该数组不再为空，因此没有NullReferenceException。
Public Class clsFamily
Public PersonName() As String
Public RelationType() As String
Public DOB() As Date
Public Gender() As String
Public Occupation() As String
Public Sub New()
PersonName = New String(0) {""}
End Sub
End Class
关于asp.net - System.NullReferenceException : Object reference not set to an instance of an object. in vb.net，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31963921/