The crude horrible way to do that is you could have on Form3, 14 different public facing properties.
public string textboxValue1;
public string textboxValue2;
public string textboxValue3;
etc...
Then when you new up Form3, you'll have access to these and pass the data that way.
so:
Form3 form3 = new Form3();
form3.textboxValue1 = fieldValue1;
form3.textboxValue2 = fieldValue2;
form3.textboxValue3 = fieldValue3;
etc..
form3.ShowModal();
form3.Dispose();
Ideally you should be using a business object / model.
You've already mentioned 14 rows and 4 columns, so your model might look something like this:
public class modelname
{
public datatype column1fieldname { get; set; }
public datatype column2fieldname { get; set; }
public datatype column3fieldname { get; set; }
public datatype column4fieldname { get; set; }
}
where datatype is string, int, decimal or whatever value types your using, and column_n_fieldname relates to something sensible in your object!
On form2 you can have a private property:
private List<modelname> capturedData;
in the constructor - new it up so:
public Form2()
{
InitializeComponent();
capturedData = new List<modelname>();
}
when the user clicks to form3, you can stuff your data from the textboxes into the model -> then pass the model to form3 to do whatever you want with it.
so on form2 you might have a couple of methods like:
private void CollectData()
{
capturedData.Clear();
AddRowData(yourrow1column1value, yourrow1column2value, yourrow1column3value, yourrow1column4value); // Row 1
AddRowData(yourrow2column1value, yourrow2column2value, yourrow2column3value, yourrow2column4value); // Row 2
// etc...
}
private void AddRowData(datatype column1data, datatype column2data, datatype column3data, datatype column4data)
{
capturedData.Add(new modelname() { column1fieldname = column1data, column2fieldname = column2data, column3fieldname = column3data, column4fieldname = column4data});
}
Form3's constructor might be:
public Form3(List<modelname> capturedData)
{
InitializeComponent();
// Then whatever you want to do with it...
}