C#如何将List<string>转换为List<double>

//string转List<double>
List<string> strList = new List<string>();
strList.Add("100"); strList.Add("500"); strList.Add("700");
List<double> douList = strList.ConvertAll(s => Convert.ToDouble(s));
string str = "600 650 700";
List<double> douList2 = str.Split(' ').ToList().ConvertAll(s => Convert.ToDouble(s));
//List<double>转string
string douStr = string.Join(" ", douList2.ConvertAll(s => Convert.ToString(s)));//douStr : 600 650 700

double num = Convert.ToDouble("3.14");
double total_battery_capacity = Convert.ToDouble(this.txtbox_battery_totoal_capacity.Text);

string str_num = Convert.ToString(3.14);
string str_battery_actual_capacity = Convert.ToString(total_battery_capacity * battery_ratio);

string str_name = this.txtbox_battery_ratio.Text;

this.txtbox_hello.Text = "hello world";
this.txtbox_run_power.Text = Convert.ToString(run_power);

this.txtbox_life_days.ForeColor = Color.Red;
this.txtbox_run_average_power.ForeColor = Color.Blue;