I create a simple calculator through the Visual Studio 2010 Express program in the Windows forms application environment. In my code, I need to prohibit the entry of letters into lines (but so that numbers and signs + - * / I could enter), (that is, when you click on a letter, the letter is not entered, or in the same txtResult (Result), it is written : Enter only digits !!!) prohibit divide by zero (ie, write in lblResult: "Division by 0 is prohibited"), prohibit entering anything in the Result line, and also, when not filling one of the lines, write in lblResult: "There is no number in one or two lines". Function code here:
private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) { }//Форма private: System::Void btnClose_Click(System::Object^ sender, System::EventArgs^ e) {this->Close(); }//Закрытие формы private: System::Void btnAdd_Click(System::Object^ sender, System::EventArgs^ e) { double i1, i2, i3; this->lblOper->Text = L"Сложение"; i1 = Convert::ToDouble(txt1->Text); i2 = Convert::ToDouble(txt2->Text); i3 = i1 + i2; this->txtResult->Text = Convert::ToString(i3); }//Складывает i1 и i2, и записывает результат в i3 private: System::Void btnReset_Click(System::Object^ sender, System::EventArgs^ e) { this->lblOper->Text = L""; this->txt1->Text = L""; this->txt2->Text = L""; this->txtResult->Text = L""; } //Сброс введеных данных private: System::Void btnSbt_Click(System::Object^ sender, System::EventArgs^ e) { double i1, i2, i3; this->lblOper->Text = L"Вычитание"; i1 = Convert::ToDouble(txt1->Text); i2 = Convert::ToDouble(txt2->Text); i3 = i1 - i2; this->txtResult->Text = Convert::ToString(i3); }//Вычитает из i1 i2, и записывает результат в i3 private: System::Void btnMlp_Click(System::Object^ sender, System::EventArgs^ e) { double i1, i2, i3; this->lblOper->Text = L"Умножение"; i1 = Convert::ToDouble(txt1->Text); i2 = Convert::ToDouble(txt2->Text); i3 = i1 * i2; this->txtResult->Text = Convert::ToString(i3); }//Умножает i1 на i2, и записывает результат в i3 private: System::Void btnDvd_Click(System::Object^ sender, System::EventArgs^ e) { double i1, i2, i3; this->lblOper->Text = L"Деление"; i1 = Convert::ToDouble(txt1->Text); i2 = Convert::ToDouble(txt2->Text); i3 = i1 / i2; this->txtResult->Text = Convert::ToString(i3); }//Делит i1 на i2, и записывает результат в i3 private: System::Void txt1_TextChanged(System::Object^ sender, System::EventArgs^ e) { } private: System::Void lbl1_Click(System::Object^ sender, System::EventArgs^ e) { } private: System::Void lblOper_Click(System::Object^ sender, System::EventArgs^ e) { } private: System::Void txtResult_TextChanged(System::Object^ sender, System::EventArgs^ e) { } 
