CODEWITHSUNDEEP
c#stringimagevisual-studioresources
casper thostrup
casper thostrup

Reputation: 1

NullExceptionError when trying to load image from Resources

I have my resources embedded in the system, the string I search for them with matches the name of the image yet I still get a ArgumentNullException... How come?

    //Check if currencies are chosen
    private void Action()
    {
        label1.Text = null;
        //Checks if items are selected then what currencies are chosen
        if (listBox1.SelectedIndex == -1 || listBox2.SelectedIndex == -1)
        {
            label1.Text = "Please select currencies";
        }
        else
        {
        LB1 = listBox1.SelectedItem.ToString();
        LB2 = listBox2.SelectedItem.ToString();
        Conversion();
        }
        pictureBox1.Image = Properties.Resources.ResourceManager.GetObject(LB1) as Image;
        pictureBox2.Image = Properties.Resources.ResourceManager.GetObject(LB2) as Image;
    }

Picture of Resource images

Thank you so much in advance!

Upvotes: 0

Views: 58

Answers (1)

John Wu
John Wu

Reputation: 52290

You've got a small logic flaw. You are setting variables inside an if condition but using them outside, even if the if condition doesn't execute.

if (listBox1.SelectedIndex == -1 || listBox2.SelectedIndex == -1)
{
    label1.Text = "Please select currencies";
}
else
{
    LB1 = listBox1.SelectedItem.ToString();  //Doesn't always run
    LB2 = listBox2.SelectedItem.ToString();
    Conversion();
}
//Always runs
pictureBox1.Image = Properties.Resources.ResourceManager.GetObject(LB1) as Image;
pictureBox2.Image = Properties.Resources.ResourceManager.GetObject(LB2) as Image;

You should probably change it to something more like this:

if (listBox1.SelectedIndex == -1 || listBox2.SelectedIndex == -1)
{
    label1.Text = "Please select currencies";
}
else
{
    LB1 = listBox1.SelectedItem.ToString();
    LB2 = listBox2.SelectedItem.ToString();
    Conversion();
    pictureBox1.Image = Properties.Resources.ResourceManager.GetObject(LB1) as Image;
    pictureBox2.Image = Properties.Resources.ResourceManager.GetObject(LB2) as Image;        }
}

Or better yet, use a guard, and use local variables, so that the compiler will catch this sort of flaw in the future:

if (listBox1.SelectedIndex == -1 || listBox2.SelectedIndex == -1)
{
    label1.Text = "Please select currencies";
    return;
}
var lb1 = listBox1.SelectedItem.ToString();
var lb2 = listBox2.SelectedItem.ToString();
Conversion(lb1, lb2);
pictureBox1.Image = Properties.Resources.ResourceManager.GetObject(lb2) as Image;
pictureBox2.Image = Properties.Resources.ResourceManager.GetObject(lb2) as Image;

Upvotes: 1

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