Help!! Excel process keep runnung export excel with Interop

You need to close and release the resources after modifying it.
you need to use try finally block and in finally block call app.Quit() method.

public void ExcelMethod()
        {
            Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
            Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
            Microsoft.Office.Interop.Excel._Worksheet worksheet1 = null;
 
            try
            {
                //Microsoft.Office.Interop.Excel._Worksheet worksheet2 = null;
                app.Visible = true;
                worksheet1 = workbook.Sheets["Sheet1"];
                worksheet1 = workbook.ActiveSheet;
                Marshal.ReleaseComObject(workbook);
                Marshal.ReleaseComObject(worksheet1);
 
                worksheet1.Cells[1, 1] = "รางงานการจัดการโครงการโดยการใช้ Program evaluation and review technique";
                worksheet1.Cells[3, 2] = "ตารางแสดงค่าต่างๆของกิจกรรมแต่ละตัวในโครงการนี้";
                Microsoft.Office.Interop.Excel.Range Chartrange = Chartrange = worksheet1.get_Range("A1", "A1");
                ;
                Chartrange.Font.Bold = true;
                GC.Collect();
                Marshal.ReleaseComObject(Chartrange);
                //GC.Collect();

 

                for (int i = 1; i < 7 + 1; i++)
                {
                    worksheet1.Cells[5, i] = dataGridView1.Columns[i - 1].HeaderText;
                    Microsoft.Office.Interop.Excel.Range kk = worksheet1.get_Range("A5", "G5");
                    Microsoft.Office.Interop.Excel.Borders borders = kk.Borders;
                    borders.LineStyle = Microsoft.Office.Interop.Excel.XlLineStyle.xlContinuous;
                    borders.Weight = 3d;
                    GC.Collect();
                    Marshal.ReleaseComObject(borders);
                    Marshal.ReleaseComObject(kk);
 
                }
                for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)
                {
                    for (int j = 0; j < 7; j++)
                    {
                        int excel_cell = dataGridView1.Rows.Count - 1 + 5;
                        if (dataGridView1.Rows[i].Cells[j].Value != null)
                        {
                            int k = i + 6;
                            worksheet1.Cells[i + 6, j + 1] = dataGridView1.Rows[i].Cells[j].Value.ToString();
                            Microsoft.Office.Interop.Excel.Range kk = worksheet1.get_Range("A" + k, "G" + k);
                            Microsoft.Office.Interop.Excel.Borders borders = kk.Borders;
                            borders.LineStyle = Microsoft.Office.Interop.Excel.XlLineStyle.xlContinuous;
                            borders.Weight = 3d;
                            GC.Collect();
                            Marshal.ReleaseComObject(borders);
                            Marshal.ReleaseComObject(kk);
                            //GC.Collect();
                            //GC.WaitForPendingFinalizers();
                        }
                        else
                        {
                            worksheet1.Cells[i + 2, j + 1] = "";
                        }
                    }
                }
            }
            finally
            {
                releaseObject(workbook);
                releaseObject(worksheet1);
 
                if (app != null)
                {
                    app.Quit();
 
                }
                releaseObject(app);
            }
        }
 
        private void releaseObject(object obj)
        {
            if (obj != null && Marshal.IsComObject(obj))
            {
                Marshal.ReleaseComObject(obj);
            }
            obj = null;
        }

[Agent_Spock]
- Added missing code brackets
[Jafarinejajadvazifehkhorani]
-I added one more solution to this question that I mustn't have done it, I should have updated the current answer.