datagridview1.currentcell=datagridview1.rows[0].cells[0]

private void tabControl1_Selecting(object sender, TabControlCancelEventArgs e)
        {
           
            if (e.TabPageIndex == 1)
                this.dataGridView1.CurrentCell = this.dataGridView1.Rows[0].Cells[0]; 
        }


 或
        private void tabControl1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if(this.tabControl1.SelectedIndex==1)
                this.dataGridView1.CurrentCell = this.dataGridView1.Rows[0].Cells[0];
        }