Object reference not set to an instance of an object

Imports System
Imports System.Data
Imports System.Drawing
Imports System.Drawing.Imaging
Partial Class _Default
Inherits System.Web.UI.Page
Private myImage As Bitmap
Private g As Graphics
Private p() As Integer = {1000000, 600000, 2500000, 80000}
Private towns() As String = {"A", "B", "C", "D"}

Private myBrushes(4) As Brush
Sub page_Load()
' Create an in-memory bitmap where you will draw the image.
' The Bitmap is 300 pixels wide and 200 pixels high.
myImage = New Bitmap(500, 300, PixelFormat.Format32bppRgb)

' Get the graphics context for the bitmap.
g = Graphics.FromImage(myImage)

' Create the brushes for drawing
myBrushes(0) = New SolidBrush(Color.Red)
myBrushes(1) = New SolidBrush(Color.Blue)
myBrushes(2) = New SolidBrush(Color.Yellow)

myBrushes(3) = New SolidBrush(Color.Green)

End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
' Variables declaration
Dim i As Integer
Dim total As Integer
Dim percentage As Double
Dim angleSoFar As Double = 0.0

' Caculates the total
For i = 0 To p.Length - 1
total += p(i)
Next

' Draws the pie chart
For i = 0 To p.Length - 1
percentage = p(i) / total * 360

g.FillPie(myBrushes(i), 25, 25, 250, 250, CInt(angleSoFar), CInt(percentage))

angleSoFar += percentage

' Draws the lengend
g.FillRectangle(myBrushes(i), 350, 25 + (i * 50), 25, 25)

' Label the towns
g.DrawString("Town " & towns(i), New Font("Verdana", 8, FontStyle.Bold), Brushes.Brown, 390, 25 + (i * 50) + 10)
Next
End Sub
End Class

In the above code which is used to generate pie chart Im getting error:object reference not set to an instance of an object at g.FillPie(myBrushes(i), 25, 25, 250, 250, CInt(angleSoFar), CInt(percentage))

Please help me out with a solution for such kind of error

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Meetu Choudhary17y ago
In Your COde
' Get the graphics context for the bitmap.
g = Graphics.FromImage(myImage)
You haven't initilaized the g object try using new keyword. in your declaration section.
Roei Bar17y ago
from the code you sent the only reasonable idea for the error is that g is null

' Get the graphics context for the bitmap.
g = Graphics.FromImage(myImage)

this might not be initialized