How to Give back a DataGridView in Winforms

Question

So, I have a project in which I allow editing of a DatagridView in a separate Form. I pass in the DatagridView object and its parent container to the constructor of the new Form.

This works well and I can edit the grid that way. But when I try to give it back by changing its parent back to the original form, I get this error :

Cannot convert type 'System.Windows.Forms.MenuItem' to 'System.Windows.Forms.Control'   

Now both MenuItem, and Manual Entry directly inherit from Form.

Here is my code that takes the DataGridView from the original form (which works correctly)

public partial class ManualEntry : Form
{
    private Data d;
    DataGridView DataView;
    MenuItem mi;

    public ManualEntry(DataGridView ExcelDisplay, Data d, MenuItem menuItem)
    {
        InitializeComponent();

        //Take the Datagridview from the MenuItem.

        DataView = ExcelDisplay;
        DataView.Parent = this;
        mi = menuItem;
        this.d = d;
        this.DataView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
        this.DataView.Location = new System.Drawing.Point(15, 76);
        this.DataView.Size = new System.Drawing.Size(237, 211);
        this.DataView.TabIndex = 5;
        this.DataView.CellContentClick += new System.Windows.Forms.DataGridViewCellEventHandler(this.DataView_CellContentClick);
    }

Now here is me trying to give it back. and of course it produces the error above.

    private void FinishButton_Click(object sender, EventArgs e)
    {
        //move the datagridview back to the original form and give its old size,shape, and position back.

        DataView.Parent = mi;
        this.DataView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
        this.DataView.Location = new System.Drawing.Point(12, 167);
        this.DataView.Name = "ExcelDisplay";
        this.DataView.Size = new System.Drawing.Size(250, 256);
        this.DataView.TabIndex = 7;
        this.Close();
    }

I have also tried casting which does not work either.

 DataView.Parent = (System.Windows.Forms.Control)mi;

Update This shows that MenuItem is a Form as well.

public partial class MenuItem : Form
{

Answer 1

This shows that MenuItem is a Form as well.

Well, you have not convinced the compiler. You can tell from the error message that it thinks that your "mi" variable is a System.Windows.Forms.MenuItem. Do not use .NET class names for your own types, that just makes your life harder to troubleshoot bugs like this. Don't use variable names like "d" either. Choosing good names is a Very Important programmer's job.

The proper way is to preserve the control's Parent property so you can set it back. Roughly:

public partial class ManualEntry : Form
{
    private Data DataViewData;
    private DataGridView DataView;
    private Point DataViewLocation;
    private Control DataViewParent;

    public ManualEntry(DataGridView ExcelDisplay, Data data)
    {
        InitializeComponent();
        this.DataViewData = data;
        this.DataView = ExcelDisplay;
        this.DataViewLocation = ExcelDisplay.Location;
        this.DataViewParent = ExcelDisplay.Parent;
        this.DataView.Parent = this;
        // etc...
    }

    protected override void OnFormClosing(FormClosingEventArgs e) {
        base.OnFormClosing(e);
        if (!e.Cancel) {
            DataView.Parent = this.DataViewParent;
            DataView.Location = this.DataViewLocation;
            // etc..
        }
    }
}