Passing a datatable from one form to another form

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i have a form1 and form2 . form2 is opened from form1 , it has a dgv after filling it, its copied to a datatable on a click button and form2 is closed or visible = false, i passed the datatable to form1 but its giving me a null reference: here is my code in form2:

C#

private void button1_Click(object sender, EventArgs e)
        {
            perclothesdescriptionDT = new DataTable();

            foreach (DataGridViewColumn col in dataGridView3.Columns)
            {
                perclothesdescriptionDT.Columns.Add(col.HeaderText);
            }

            foreach (DataGridViewRow row in dataGridView3.Rows)
            {
                DataRow dRow = perclothesdescriptionDT.NewRow();
                foreach (DataGridViewCell cell in row.Cells)
                {
                    dRow[cell.ColumnIndex] = cell.Value;
                }
                perclothesdescriptionDT.Columns.RemoveAt(0);
                perclothesdescriptionDT.Rows.Add(dRow);
            }
            this.Visible = false;

        }

        public DataTable mydt
        {
            get
            {
                return perclothesdescriptionDT;
            }
        }

In form1 :

C#

form2= new Form2();

                cmd1.CommandText = "insert into [dbo].[personClothesDesc](upperPart, lowerPart, belt, socks, shoes, differentSigns) values (@upperPart, @lowerPart, @belt, @socks, @shoes, @differentSigns)";
                        for (int i = 0; i < form2.mydt.Rows.Count; i++)
                        {
                            cmd1.Parameters.Clear();
                            cmd1.Parameters.AddWithValue("@upperPart", form2.mydt.Rows[i].ItemArray.GetValue(5).ToString());
                            cmd1.Parameters.AddWithValue("@lowerPart", form2.mydt.Rows[i].ItemArray.GetValue(4).ToString());
                            cmd1.Parameters.AddWithValue("@belt", form2.mydt.Rows[i].ItemArray.GetValue(3).ToString());
                            cmd1.Parameters.AddWithValue("@socks", form2.mydt.Rows[i].ItemArray.GetValue(2).ToString());
                            cmd1.Parameters.AddWithValue("@shoes", form2.mydt.Rows[i].ItemArray.GetValue(1).ToString());
                            cmd1.Parameters.AddWithValue("@differentSigns", form2.mydt.Rows[i].ItemArray.GetValue(0).ToString());
                            cmd1.ExecuteNonQuery();
                        }

What I have tried:

i have to tried to pass the datatable from form2 to form1 but its giving me null reference :
public DataTable mydt
{
get
{
return perclothesdescriptionDT;
}
}

Posted 6-Jul-16 3:14am

ramy nemer

Updated 6-Jul-16 9:57am

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Daniel Jones 7-Jul-16 1:58am

Take a look at this link: http://stackoverflow.com/questions/1559770/send-values-from-one-form-to-another-form

3 solutions

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OriginalGriff · Answer 1 · 2016-07-06T03:27:00

Well yes...it will.
You create the instance of Form2, and immediately use the property:

C#

form2= new Form2();
cmd1.CommandText = ...
for (int i = 0; i < form2.mydt.Rows.Count; i++)
{
    cmd1.Parameters.Clear();
    cmd1.Parameters.AddWithValue("@upperPart",
         form2.mydt.Rows[i].ItemArray.GetValue(5).ToString());
    ...

But your code for Form2 shows the database only being filled when the user clicks a button.
Since you don't even show the form to the user, much less give him time to press a button the datatable is never created and the property can only return null.
Probably what you are trying to do is access the existing on-screen instance of Form2 that you created and displayed elsewhere - in which case you need to have stored the instance in a class level variable in Form1 and use the property from that instance rather than creating a new one.

Vignesh Mani · Answer 2 · 2016-07-06T04:44:00

Solution 2

Hi Please refer below link it will help to you.

How to Pass Data One Form to Another in Windows Form Application[^]

Posted 6-Jul-16 4:44am

Vignesh Mani

Comments

ramy nemer 6-Jul-16 11:58am

no this doesnt work for me , the values are in form2 ,i need to pass them to form1 to use it to insert to databaseto

ramy nemer 6-Jul-16 11:58am

i think the best way is to use a public class but i dont know how

BillWoodruff · Answer 3 · 2016-07-06T09:57:00

I suggest: in the second Form with the DataGridView

define a Public Action (delegate) that returns a DataTable:

C#

public Action<DataTable> SendDataTable;

In the Click EventHandler for the Button on the second Form, after the DataTable is constructed, then invoke the delegate (Action) with the DataTable as the parameter value:

C#

private void btnTransmitDataTable_Click(object sender, EventArgs e)
{
    // build the DataTable

    // invoke the Action delegate
    if(SendDataTable != null) SendDataTable(perclothesdescriptionDT);
}

In the Main Form (that creates the Form with the DataGridView):

C#

// in Main Form scope
Form2 form2;

// in an appropriate EventHandler ... Form_Load ?
form2= new Form2();
form2.SendDataTable += HandleDztaTableResult;

private void HandleDataTableresult(DataTable dataTable)
{
    // do whatever with the data

    // Dispose, Close, or Hide secondary Form ?
}

There are many ways you could address this issue of form-to-form data transfer. You could, for example, create the instance of the DataTable and inject it into the instance of Form2; you could pass in the instance of the DataTable by reference as a parameter to a method in the secondary Form, etc.

OriginalGriff has an excellent series of three articles on different approaches to transferring information from form to form; I suggest you read them; here's a link to the first, which has links to the other two in the series: [^].

Passing a datatable from one form to another form

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