Error Object reference not set to an instance of an object.

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1.00/5 (1 vote)

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VB

Public Class Form1
    Dim a As Double
    Dim b As Double
    Dim c As Double
    Dim x As ClassLibrary1.Class1 // creating object

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        a = Integer.Parse(TextBox1.Text)
        b = Integer.Parse(TextBox2.Text)
        TextBox3.Text = CStr(x.add(a, b)) //calling the value and print in textbox3
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Label1.Text = x.time() //calling the value and print in lablel
    End Sub
End Class

class Library

Public Class Class1
    Private c As Double
    Private a As DateTime
    Dim b As DateTime

    ReadOnly Property add(ByVal a As Double, ByVal b As Double)
        Get
            c = a + b
            Return CStr(c)
        End Get
    End Property
    ReadOnly Property time()
        Get
            a = Today
            b = Now()
            Return CStr(b)
        End Get
    End Property
End Class

Posted 5-May-14 23:01pm

Kamal kannan D

Updated 5-May-14 23:08pm

Vedat Ozan Oner

v2

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Comments

Manas Bhardwaj 6-May-14 5:06am

This is not a good question.

What is the problem and what have you tried?

For the error message, it's quite clear that somewhere you have a null object and you are trying to access it.

Vedat Ozan Oner 6-May-14 5:11am

error says what happened. use the debugger to find where you get this error. https://www.google.com.tr/#q=object+reference+not+set+to+an+instance+of+an+object

Sanket Saxena 6-May-14 5:17am

Dim x As ClassLibrary1.Class1 // creating object
This does not create any object.

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OriginalGriff · Answer 1 · 2014-05-05T23:12:00

Look at your code:

VB

Dim x As ClassLibrary1.Class1 // creating object
...
Label1.Text = x.time() //calling the value and print in lablel

That doesn't "creating object" - it allocates a variable called "x" that can refer to an object. It doesn't create any object and assign the value to "x", it creates x and assigns Nothing to it.
Probably, what you want to say is:

VB

Dim x As New ClassLibrary1.Class1 // creating object