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POnullreferenceexception in C# with nested for loop
 

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  1. POnullreferenceexception in C# with nested for loop
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    <p>while I'm developing an application that does some calculations for the image it raises a nullreferenceexception at the beginning of the for loop </p> <p>the application is windows form application </p> <p>here is the code</p> <p>=========================================</p> <pre><code>using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Drawing.Drawing2D; namespace HistgramApp { public partial class Form1 : Form { Image img; Bitmap image; int temp; int r = 0, g = 0, b = 0; public Form1() { InitializeComponent(); this.Text = "HistogramApp"; this.AutoScroll = true; } //Generate new image dimensions public Size GenerateImageDimensions(int currW, int currH, int destW, int destH) { //double to hold the final multiplier to use when scaling the image double multiplier = 0; //string for holding layout string layout; //determine if it's Portrait or Landscape if (currH &gt; currW) layout = "portrait"; else layout = "landscape"; switch (layout.ToLower()) { case "portrait": //calculate multiplier on heights if (destH &gt; destW) { multiplier = (double)destW / (double)currW; } else { multiplier = (double)destH / (double)currH; } break; case "landscape": //calculate multiplier on widths if (destH &gt; destW) { multiplier = (double)destW / (double)currW; } else { multiplier = (double)destH / (double)currH; } break; } //return the new image dimensions return new Size((int)(currW * multiplier), (int)(currH * multiplier)); } //Resize the image private void SetImage(PictureBox pb) { try { //create a temp image Image img = pb.Image; //calculate the size of the image Size imgSize = GenerateImageDimensions(img.Width, img.Height, this.pictureBox1.Width, this.pictureBox1.Height); //create a new Bitmap with the proper dimensions Bitmap finalImg = new Bitmap(img, imgSize.Width, imgSize.Height); //create a new Graphics object from the image Graphics gfx = Graphics.FromImage(img); //clean up the image (take care of any image loss from resizing) gfx.InterpolationMode = InterpolationMode.HighQualityBicubic; //empty the PictureBox pb.Image = null; //center the new image pb.SizeMode = PictureBoxSizeMode.CenterImage; //set the new image pb.Image = finalImg; } catch (System.Exception e) { MessageBox.Show(e.Message); } } //Sample usage private void folderBrowserDialog1_HelpRequest(object sender, EventArgs e) { } private void button1_Click(object sender, EventArgs e) { OpenFileDialog ofd = new OpenFileDialog(); if (ofd.ShowDialog() == DialogResult.OK ) { String sourcefile = ofd.FileName; String sourcefolder = Path.GetDirectoryName(ofd.FileName); // pictureBox1.ImageLocation = sourcefile; img = Image.FromFile(sourcefile); pictureBox1.Image = img; // pictureBox1.Height = img.Height; // pictureBox1.Width = img.Width; Size imgsize = GenerateImageDimensions(img.Width, img.Height, pictureBox1.Width, pictureBox1.Height); // Loop through the images pixels to reset color. } } private void Form1_Scroll(object sender, ScrollEventArgs e) { } private void saveFileDialog1_FileOk(object sender, CancelEventArgs e) { } private void Form1_Load(object sender, EventArgs e) { } private void pictureBox1_Click(object sender, EventArgs e) { } private void pictureBox1_SizeChanged(object sender, EventArgs e) { } private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e) { } public void calc() { int i, j; i = 0; j = 0; // HERE IS THE EXCEPTION!! for ( i = 0; i &lt; 22; i++) { for ( j = 0; j &lt; 22; j++) { Color pixelColor = image.GetPixel(i, j); if (textBox1.Text == pixelColor.R.ToString()) { r++; } if (textBox1.Text == pixelColor.G.ToString()) { g++; } if (textBox1.Text == pixelColor.B.ToString()) { b++; } else ; } } label4.Text = r.ToString(); label5.Text = g.ToString(); label6.Text = b.ToString(); } private void button2_Click(object sender, EventArgs e) { calc(); } private void label6_Click(object sender, EventArgs e) { } } } </code></pre>
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    1. USMethodMan
    1. USHazem Taha
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      1. POnullreferenceexception in C# with nested for loop
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    2. VO
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      1. VTDownMod
    1. COThis is not a free debugging service.
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      1. USOndrej Tucny
    2. COYou never assigned anything to `image`. Maybe you meant `img`?
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      1. POnullreferenceexception in C# with nested for loop
      1. UStjameson
    3. COthank U very much Tomasz :) and sorry for the poor post , it's just my first one .
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      1. POnullreferenceexception in C# with nested for loop
      1. USHazem Taha
 

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