How to build a string correctly?

Question

C++ / C#

There is a form

There are two GroupBox with ComboBox and TextBox

var startCompoundsList = startCompounds.Controls.OfType<ComboBox>();  // Список ComboBox начала реакции
    var endCompoundsList = endCompounds.Controls.OfType<ComboBox>();    // Список ComboBox конца реакции
    var startMultipleList = startCompounds.Controls.OfType<TextBox>();           // Список TextBox начала реакции
    var endMultipleList = endCompounds.Controls.OfType<TextBox>();              // Список TextBox конца реакции

Based on the selected ComboBox, it is necessary to visually display the reaction: Following the example of the picture, it should come out: The catch is that the intermediate ComboBox and TextBox can be empty and it is necessary that it does not turn out like: 1γAl2O3+ 1+ 2SiO2(β-quartz)+2H2O = Al2O3 2SiO2 2H2O 1+1+1+ How to implement this?
reactionText.Text = "";
γAl2O3+2SiO2(β-кварц)+2H2O = Al2O3·2SiO2·2H2O

Answer 1

StringBuilder sb = new StringBuilder();
 sb.Append("первая");
 sb.Append("вторая");
if(value != 1)  sb.Append("строка не равная 1");

 sb.Append("третья");

https://docs.microsoft.com/ru-ru/dotnet/api/system...