c# - If else statement textbox error -

i trying create if else statement show message box if no input.

if(textbox1.text==false) {    messagebox.show("please fill in boxes") } 

i have 16 different text box out, need use if else statement each?

pass textboxes in list , loop it

//create list once in constructor of main form or window list<textbox> list = new list<textbox>()  //... list.add(textbox1); list.add(textbox2);' //...  loop  foreach(textbox txt in list) {     if(string.isnullorwhitespace(txt.text))     {         messagebox.show("please fill in boxes");         break;     } } 

update
if textboxes expecting number/double input use tryparse checking if value valid

foreach(textbox txt in list) {     double temp;     if(double.tryparse(txt.text, temp) == true)     {         //save or use valid value          debug.print(temp.tostring());     }     else     {         messagebox.show("please fill in boxes");         break;     } }