Array of Runtime Labels

This is a discussion on Array of Runtime Labels within the C# Programming forums, part of the General Programming Boards category; Using C# 2005, I am trying to create labels at run-time using an array. The code below WITHOUT the array ...

  1. #1
    Polar Fuzz
    Join Date
    Oct 2003
    Posts
    36

    Array of Runtime Labels

    Using C# 2005, I am trying to create labels at run-time using an array. The code below WITHOUT the array does work without run-time errors:

    Code:
    namespace sud
    {
        public partial class sud : Form
        {
            private Label labelTest = new Label();
    
            public sud()
            {
                InitializeComponent();
            }
    
            private void sud_Load(object sender, EventArgs e)
            {
                this.labelTest.Size = new System.Drawing.Size(50, 50);
                this.labelTest.Location = new System.Drawing.Point(40, 40);
                this.labelTest.Name = "cellTest";
                this.labelTest.Text = "Test";
                this.Controls.Add(labelTest);
            }
          
        } // end partial class: sud
    
    } // end namespace: sud
    I get this error ONLY at run-time: object reference not set to an instance of an object if I use the code below which uses an ARRAY to create the labels.

    Code:
    namespace sud
    {
        public partial class sud : Form
        {
            private Label[] labelTest2;
    
            public sud()
            {
                InitializeComponent();
            }
    
            private void sud_Load(object sender, EventArgs e)
            {
                this.labelTest2 = new Label[10];
                this.labelTest2[0].Size = new System.Drawing.Size(50, 50);
                this.labelTest2[0].Location = new System.Drawing.Point(40, 40);
                this.labelTest2[0].Name = "cellTest";
                this.labelTest2[0].Text = "Test";
                this.Controls.Add(labelTest2[0]);
            }
          
        } // end partial class: sud
    
    } // end namespace: sud
    Suggestions?

  2. #2
    Registered User valaris's Avatar
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    Add labelTest2[0] = new Label();

    before you call its properties.

    You've created an array of 10 Labels, not 10 Labels.

  3. #3
    Polar Fuzz
    Join Date
    Oct 2003
    Posts
    36
    I still got the same error but I did manage to get it to work from that suggestion. Changes in blue:

    Code:
    namespace sud
    {
        public partial class sud : Form
        {
            private Label[] labelTest2;
    
            public sud()
            {
                InitializeComponent();
                labelTest2 = new Label[10];
            }
    
            private void sud_Load(object sender, EventArgs e)
            {
                this.labelTest2[0] = new Label();
                this.labelTest2[0].Size = new System.Drawing.Size(50, 50);
                this.labelTest2[0].Location = new System.Drawing.Point(40, 40);
                this.labelTest2[0].Name = "cellTest";
                this.labelTest2[0].Text = "Test";
                this.Controls.Add(labelTest2[0]);
            }
          
        } // end partial class: sud
    
    } // end namespace: sud
    Thanks for your help!

  4. #4
    Registered User valaris's Avatar
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    Jun 2008
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    507
    Yup.

    You had 10 references to a label.

    It's analgous to in C++ creating 10 pointers to something and trying to access an element of it. It's not going to fly unless you allocate memory to it.

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