Drag n drop fails - Object reference not set to an instance of an object

[Jonas Andersson]

I did follow a Drag N Drop tutorial on YouTube, did exactly the same thing but I get the error:

"Object reference not set to an instance of an object".

The difference would be that I do create the DataGridView in code behind. Also theres several of them. One in each tab.

How do I adjust my code to make it work?

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
tabControl1.TabPages.Clear();
createGridViews();
}

private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
dgwDynamic.Columns["Column1"].Visible = false;
}

DataGridView dgwDynamic;
private void createGridViews()
{
int pageNumber = 0;
for (int i = 0; i < 3; i++)
{
//Populate DataGridView.

/* Dynamic DataGridView */
dgwDynamic = new DataGridView();
dgwDynamic.Name = "DataGridView" + i.ToString();
dgwDynamic.ScrollBars = ScrollBars.Both;
dgwDynamic.Dock = DockStyle.Fill;

/* Dynamic TabPage */
TabPage tpDynamic = new TabPage();
pageNumber = i + 1;
tpDynamic.Name = "tabPage" + pageNumber.ToString();

string tabName = "TabPage" + pageNumber.ToString();

tpDynamic.Text = tabName;

tpDynamic.TabIndex = i;
// One newGridView per newTabPage
tpDynamic.Controls.Add(dgwDynamic); // Add Dynamic DataGridView to Dynamic TabPage
tabControl1.Controls.Add(tpDynamic); // Add Dynamic TabPage to TabControl
dgwDynamic.DataSource = GetTable(); // Add DataTable to Dynamic DataGridView
/* Drag N Drop EventHandler */
dgwDynamic.CellMouseDown += new System.Windows.Forms.DataGridViewCellMouseEventHandler(this.dgwDynamic_CellMouseDown);

}//End for loop
}

private static DataTable table;
static DataTable GetTable()
{
// Here we create a DataTable with four columns.
table = new DataTable();
table.Columns.Add("Column1", typeof(string));
table.Columns.Add("Column2", typeof(string));
table.Columns.Add("Column3", typeof(string));


// Here we add five DataRows.
table.Rows.Add("Col1_Row1", "Col2_Row1", "Col3_Row1");
table.Rows.Add("Col1_Row2", "Col2_Row2", "Col3_Row2");
table.Rows.Add("Col1_Row3", "Col2_Row3", "Col3_Row3");
table.AcceptChanges();
return table;
}

private void dgwDynamic_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
{
//To Copy the data selected
dgwDynamic.DoDragDrop(dgwDynamic.CurrentCell.Value.ToString(), DragDropEffects.Copy);
// ERROR: Object reference not set to an instance of an object
}

private void listBox1_DragEnter(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.Text))
e.Effect = DragDropEffects.Copy;
else
e.Effect = DragDropEffects.None;
}

private void listBox1_DragDrop(object sender, DragEventArgs e)
{
listBox1.Items.Add(e.Data.GetData(DataFormats.Text));
}

}

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