去除空白字元 Replace、Trim

//去除字串裡面的空白(或任意)字元用 replace 去除 
GridView1.Rows[i].Cells[5].Text.ToString().Replace(" ","")
GridView1.Rows[i].Cells[5].Text.ToString().Replace("hollo","hello") // hollo -> hello

//去除字串前後空白 Trim
GridView1.Rows[i].Cells[5].Text.ToString().Trim()