Question

I am trying to update a SQL databound combobox with new information from a new form. After I make the adds/edits and save on the popup form, I want to refresh the combobox with the new info and select the currently added/edited item. Currently, the code below refreshes the list, but will not modify “myID” on the parent form as I thought a reference variable should. How can I most efficiently do this? I have about 20 forms to do a similar type thing.

In form1

    int newid = 0;
    private void addToolStripMenuItem1_Click(object sender, EventArgs e)
    {
        CoalSeamsForm csf = new CoalSeamsForm(ref newid);
        csf.ShowDialog();
        coalSeamsTableAdapter.Fill(well_Information2DataSet.CoalSeams);
        coalSeamsBindingSource.Find("CoalSeamID", newid);
    }

In form 2

    int myID = 0;

    public CoalSeamsForm(ref int myId)
    {
        this.myID = myId;
        InitializeComponent();
    }

    private void CoalSeamsForm_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (!isOK)
        {
            if (DialogResult.Yes == MessageBox.Show("Would you like to save the changes?", "Confirm", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
            {
                Save();
                DataRowView drv = (DataRowView)coalSeamsBindingSource.Current;
                myID = (int)drv["CoalSeamID"];
            }
        }
    }
}

Answer 1

Reference parameters only work within the calling method/constructor. Once they are outside of that individual method, they become copies within the second object. To implement, from the suggestions of Steve and others, I used a public property and accessed it from the first form. Also, I used a databound combobox in the posted code, which is a more typical application from me vs. setting the BindingSource.Position property.

In form1

private void addEditCoalSeams(bool isAdd)
    {
        int? myId=null;
        if (!isAdd)
        {
            myId = (int?)coalSeamsComboBox.SelectedValue;
        }

        using (CoalSeamsForm csf = new CoalSeamsForm(myId, isAdd))
        {
            if (DialogResult.OK == csf.ShowDialog())
            {
                coalSeamsTableAdapter.Fill(well_Information2DataSet.CoalSeams);
                coalSeamsComboBox.SelectedValue = csf.coalID;
            }
        }
    }

In CoalSeamsForm

    public int? coalID {get; set;}
    bool isAdd = false;

    public CoalSeamsForm(int? coalId, bool isAdd)
    {
        this.coalID = coalId;
        this.isAdd = isAdd;
        InitializeComponent();
    }

    private void okButton_Click(object sender, EventArgs e)
    {
        Save();
        DataRowView drv = (DataRowView)coalSeamsBindingSource.Current;
        this.coalID = (int)drv["CoalSeamID"];
        this.DialogResult = DialogResult.OK;
    }