how can handle event in grid view button in win form

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C#

here, in my win project ,have button "update Subject" in data grid view (dgv) in form

and add event on clicked at this button open a popup win to update Subject (content Field)
here, problem is when i clicked button, multiple win is opened .

and also when i clicked btndelete multiple row are delete

how can i solve it

my code is

private void Subjectseup()
       {
           gvsubjectsetup.DataSource = null;
           try
           {
               string querystring = "SELECT * FROM dbo.Subjects";
               DataTable datatable = Class1.Datatablebind(querystring);
               if (datatable.Rows.Count > 0)
               {
                   gvsubjectsetup.AutoGenerateColumns = false;

                   //Set Columns Count
                   gvsubjectsetup.ColumnCount = 8;

                   //Add Columns
                   gvsubjectsetup.Columns[0].Name = "Subjectid";
                   gvsubjectsetup.Columns[0].HeaderText = "Subject Id";
                   gvsubjectsetup.Columns[0].DataPropertyName = "Subject_id";

                   gvsubjectsetup.Columns[1].HeaderText = "Subject Name";
                   gvsubjectsetup.Columns[1].Name = "Subject";
                   gvsubjectsetup.Columns[1].DataPropertyName = "Subject Name";

                   gvsubjectsetup.Columns[2].HeaderText = "Allow Class";
                   gvsubjectsetup.Columns[2].Name = "AllowClass";
                   gvsubjectsetup.Columns[2].DataPropertyName = "Allow Class";

                   gvsubjectsetup.Columns[3].Name = "SubjectType";
                   gvsubjectsetup.Columns[3].HeaderText = "Subject Type";
                   gvsubjectsetup.Columns[3].DataPropertyName = "Subject Type";

                   gvsubjectsetup.Columns[4].HeaderText = "Subject Valuation";
                   gvsubjectsetup.Columns[4].DataPropertyName = "Subject valuation";

                   gvsubjectsetup.Columns[5].HeaderText = "Create Date";
                   gvsubjectsetup.Columns[5].DataPropertyName = "Create date";

                   gvsubjectsetup.Columns[6].HeaderText = "Category";
                   gvsubjectsetup.Columns[6].DataPropertyName = "category";

                   // add a button column.
                   DataGridViewButtonColumn updatebutton = new DataGridViewButtonColumn();

                   DataGridViewButtonColumn deletbutton = new DataGridViewButtonColumn();

                   updatebutton.HeaderText = "Update Classes";
                   updatebutton.Text = "Update";
                   updatebutton.Name = "btnUpdate";

                   deletbutton.HeaderText = "Delete Classes";
                   deletbutton.Text = "Delete";
                   deletbutton.Name = "btnDelete";

                   updatebutton.UseColumnTextForButtonValue = true;
                   deletbutton.UseColumnTextForButtonValue = true;
                   // addsectionbutton.UseColumnTextForButtonValue = true;

                   gvsubjectsetup.Columns.Add(updatebutton);
                   //  gvsubjectsetup.Columns.Add(addsectionbutton);
                   gvsubjectsetup.Columns.Add(deletbutton);

                   // ADD click event on button

                   gvsubjectsetup.CellClick += new DataGridViewCellEventHandler(gvsubjectsetup_click);
                   // gvsubjectsetup.DataSource = datatable;
                   gvsubjectsetup.DataSource = new BindingSource(datatable, null);
               }
               else
               {
                   return;
               }
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message);
           }
       }

//here i handle event

public void gvsubjectsetup_click(object sender, DataGridViewCellEventArgs e)
       {
           try
           {
               Int32 id = 0;

              if (gvsubjectsetup.Columns[e.ColumnIndex] is DataGridViewButtonColumn && e.RowIndex >= 0)


              {
                   if ((e.RowIndex > 0) || (e.ColumnIndex == gvsubjectsetup.Columns["btnUpdate"].Index) || (e.ColumnIndex == gvsubjectsetup.Columns["btnDelete"].Index))
                   {
                       if (e.ColumnIndex == gvsubjectsetup.Columns["btnUpdate"].Index)

                       {
                           id = (Int32)gvsubjectsetup[0, e.RowIndex].Value;
                           string s = "update subject";

                           Subjectpopwindows popwin = new Subjectpopwindows(s, id);
                           popwin.Show();

                       }
                       else if (e.ColumnIndex == gvsubjectsetup.Columns["btnDelete"].Index)
                       {
                           int subneme = (Int32)gvsubjectsetup[0, e.RowIndex].Value;

                           {
                               DialogResult result = MessageBox.Show("Do You Want to delete Class " + subneme + "?", "Delete", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                               if (result.Equals(DialogResult.OK))
                               {
                                   string delete = "  DELETE FROM dbo.Subjects WHERE Subject_id='" + subneme + "'";
                                   Class1.insertrecord(delete);
                                   MessageBox.Show("Delete Successfully !");
                                   Subjectseup();
                                   return;
                               }
                               else
                               {
                                   return;
                               }
                           }
                       }
                       else
                           return;
                   }
                   else
                   {
                       return;
                   }

               }
               else
               {
                   return;
               }
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message);
               return;
           }
       }