How to concatenate numbers in c++/CLR - c++-cli

Question

I have a variable num1.
Now I would like to concatenate a number to num1
Example -> num1 += 5;
Rather than concatenating like expected, it sets num1 as 0. Same goes for num2
This is my part of code that should set num1 or num2 as 5:
private: System::Void button14_Click(System::Object^ sender, System::EventArgs^ e) {
if (label1->Text == "Operator")
{
if (label3->Text == "Result")
label3->Text = gcnew String("5");
else
label3->Text += gcnew String("5");
to_string(num1) += "5";
}
else if (label1->Text != "Operator")
{
label3->Text += gcnew String("5");
to_string(num2) += "5";
}
}
This is the = button
private: System::Void button23_Click(System::Object^ sender, System::EventArgs^ e) {
if (label1->Text != "Operator")
{
if (label1->Text == "+")
{
result = num1 + num2;
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "-")
{
result = num1 - num2;
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "x")
{
result = num1 * num2;
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "÷")
{
float(result) = num1 / num2;
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "%")
{
float(result) = num1 / num2 * 100;
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "Power")
{
result = pow(num1, num2);
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "Square Root")
{
result = sqrt(num1);
label3->Text = gcnew String(to_string(result).data());
}
else if (label1->Text == "Cube Root")
{
result = cbrt(num1);
label3->Text = gcnew String(to_string(result).data());
}
}
else
{
label1->Text = "Please make sure you complete the equation(put 0 as";
label3->Text = "2nd number for root)";
}
}

Answer 1

num1 += 6 is the same as num1 = num1 + 6 so, if num1 is 5, it is the same as num1 = 5 + 6, and as you probably know, 5 + 6 is 11.
to_string(num1) += "5"; has no effect on num; it creates a string, modifies it, and then throws it away.
You need to use the Ancient Power of Mathematics: num = num * 10 + 5;