高手帮我看看这个ADO.NET的连接有什么错

除了insert语句可以成功以外，updata还有delete语句执行时提示语句都是有的，但是没有对数据库进行任何操作，谢谢
private void btnAdd_Click(object sender, System.EventArgs e)
{
    insCmd= "insert into FlightDetails values ('"+this.txtFlightCode.Text+"','"+this.txtAirline.Text+"','"+this.txtDestination.Text+"','"+this.txtSource.Text+"','"+this.txtArrival.Text+"','"+this.txtDeparture.Text+"','"+this.cboSeats.SelectedItem.ToString()+"')"; objSqlcommend=new SqlCommand(insCmd,objSqlconnection); try
{
objSqlconnection.Open();
objSqlcommend.ExecuteNonQuery();
MessageBox.Show("添加成功");

this.btnModify.Enabled=true;
this.btnDelete.Enabled=true;
this.btnAdd.Enabled=false;
this.txtFlightCode.Enabled=false; }
catch (SqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
objSqlconnection.Close();
}

}
private void btnModify_Click(object sender, System.EventArgs e)
{
modCmd="update FlightDetails set Airline= 
                        '"+this.txtAirline.Text+ "',
                       Destination='"+this.txtDestination.Text+"',
                       Source='"+this.txtSource.Text+"',
                       Arrival='"+this.txtArrival.Text+"',
                       Departure='"+this.txtDeparture.Text+"',
                      TotalSeats="+this.cboSeats.SelectedItem.ToString()   +"where Flightcode like'"+this.txtFlightCode.Text+"'"; objSqlcommend=new SqlCommand(modCmd,objSqlconnection); try
{
objSqlconnection.Open();
objSqlcommend1.ExecuteNonQuery();
MessageBox.Show("数据已经更新");
}
catch(SqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
objSqlconnection.Close();
}
} private void btnDelete_Click(object sender, System.EventArgs e)
{
delCmd="delete from FlightDetails where FlightCode like '"+this.txtFlightCode.Text+"'";
objSqlcommend=new SqlCommand(delCmd,objSqlconnection);
try
{
DialogResult objDialogResult=MessageBox.Show("确定要删除么？","确认",MessageBoxButtons.YesNo);
if (objDialogResult.Equals(DialogResult.Yes))
{
     objSqlconnection.Open();
     objSqlcommend.ExecuteNonQuery();
     MessageBox.Show("纪录已删除");
     btnDelete.Enabled=false;
     btnAdd.Enabled=true;
     txtFlightCode.Enabled=true;
}
}
catch(SqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
objSqlconnection.Close();
}
}