Question

I am trying to create a datagridview on an event. But I have ran into strange error.

System.NullReferenceException was unhandled Message=Object reference
not set to an instance of an object.

A part of a code:

        //Creating table
        System::Windows::Forms::DataGridView^  dataGridView1;
        System::Windows::Forms::DataGridViewTextBoxColumn^  Column1;
        System::Windows::Forms::DataGridViewTextBoxColumn^  Column2;

        dataGridView1 = (gcnew System::Windows::Forms::DataGridView());

        // 
        // dataGridView1
        // 
        dataGridView1->AllowUserToAddRows = false;
        dataGridView1->AllowUserToDeleteRows = false;
        dataGridView1->ColumnHeadersHeightSizeMode = System::Windows::Forms::DataGridViewColumnHeadersHeightSizeMode::AutoSize;
        dataGridView1->Columns->AddRange(gcnew cli::array< System::Windows::Forms::DataGridViewColumn^  >(2) {Column1, 
            Column2});

The error is shown in the last line of the code above.
It seams to be that I have made mistake while defining an object or have forgotten to define something something else.

Where have I made a mistake?

I am using Visual studio 2010 and working on a Windows frames project.

Answer 1

Your column objects are declared but not instantiated. You need to gcnew them like dataGridView1. You’re getting a NullReference exception because you’re working with uninstantiated objects on that last line. Adjust your code like this:

// ...
dataGridView1 = (gcnew System::Windows::Forms::DataGridView());
Column1 = (gcnew System::Windows::Forms::DataGridViewTextBoxColumn());
Column2 = (gcnew System::Windows::Forms::DataGridViewTextBoxColumn());
// ...