C#'s easiest way to close child form and update parent form

private void simpleButton1_Click(object sender, EventArgs e)
{
();
}

public DataTable CreateTable()
{
DataTable tableA1 = new DataTable();
(new DataColumn[] { new DataColumn("name"), new DataColumn("Specification"), new DataColumn("Single Number"), new DataColumn("Quantity") });
(new object[] { "spiral", "LS-X", "111", "2" });
(new object[] { "Spiral", "LS-X", "222", "1" });
(new object[] { "Pointer", "LX-3", "523", "2" });
(new object[] { "Other", "L-1", "666", "2" });
(new object[] { "Other", "L-1", "456", "1" });
(new object[] { "Other", "L-1", "990", "2" });
return tableA1;
}