How do I prevent the same number from being entered in C# Form Textbox RSS

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  RawShed

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  How do I prevent the same number from being entered in C# Form Textbox

  Apr 26, 2020 12:55 AM|RawShed|LINK

  I made a number guessing game but there is a problem. When the same number was entered in the Textbox, I thought of printing an error message with the MessageBox, but I could not. I tried Contain and IndexOf but it didn't. For example, I entered the number 1 in the textbox first, how can I prevent entering the number 1 again?
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  mgebhard

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  Re: How do I prevent the same number from being entered in C# Form Textbox

  Apr 26, 2020 01:22 PM|mgebhard|LINK

  RawShed

  I made a number guessing game but there is a problem. When the same number was entered in the Textbox, I thought of printing an error message with the MessageBox, but I could not. I tried Contain and IndexOf but it didn't. For example, I entered the number 1 in the textbox first, how can I prevent entering the number 1 again?

  Pretty simple.  Write code that keeps track of the the numbers entered by adding he number to a list.  Check if the number exists in the list.   If you have already written the code and the code is not functioning as expected and you want a community code review, then share the code.

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  Kulrom

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  Re: How do I prevent the same number from being entered in C# Form Textbox

  Apr 26, 2020 05:33 PM|Kulrom|LINK

  RawShed

  I made a number guessing game but there is a problem. When the same number was entered in the Textbox, I thought of printing an error message with the MessageBox, but I could not. I tried Contain and IndexOf but it didn't. For example, I entered the number 1 in the textbox first, how can I prevent entering the number 1 again?

          private void MoveToTheNextQuestion()
          {
              previousAnswers.Clear();
              MessageBox.Show("Correct answer! Get ready for a new question.");            
          }
  
          private bool IsAnswerCorrect(char answer)
          {
              var result = false;           
              char randomAnswer = '3';
              if (randomAnswer == answer)            
                  result = true;         
  
              return result;
          }
  
          List<char> previousAnswers = new List<char>();
          private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
          {
              
              // get the new answer
              var newAnswer = e.KeyChar;
              
              if (char.IsDigit(newAnswer) || char.IsControl(newAnswer))
              {
                 if(previousAnswers.Count > 0)
                  {
                      // get the previous answer
                      var previousAnswer = previousAnswers.Last();                    
                      if(previousAnswer == newAnswer)
                      {                        
                          //-- ignore the answer
                          e.Handled = true;
                      }
                      else
                      {
                          previousAnswers.Add(newAnswer);
                          //-- check the correctness of the answer
                          if (IsAnswerCorrect(newAnswer) == true)
                              //-- move to the next question
                              MoveToTheNextQuestion();
                          else
                              //-- allow them to try again
                              textBox1.Text = string.Empty;
                          
                      }
                  }
                  else
                  {
                      previousAnswers.Add(newAnswer);
                      //-- check the correctness of the answer
                      if (IsAnswerCorrect(newAnswer) == true)
                          //-- move to the next question
                          MoveToTheNextQuestion();
                      else
                          //-- allow them to try again
                          textBox1.Text = string.Empty;
  
                  }
              }
              else
              {
                  // disable non-numeric entries
                  e.Handled = true;
              }
          }

  HTH

  Remember to click Mark As Answer when you get a reply which answers your question.
  My website: ASP.NET Custom Software Development
  
• • Reply
  samwu

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  Re: How do I prevent the same number from being entered in C# Form Textbox

  Apr 27, 2020 07:42 AM|samwu|LINK

  Hi RawShed,

  RawShed

  . When the same number was entered in the Textbox, I thought of printing an error message with the MessageBox, but I could not. I tried Contain and IndexOf but it didn't. For example, I entered the number 1 in the textbox first, how can I prevent entering the number 1 again?

  Can you show me you code?

  I made demo for you as a reference.

  <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
  <asp:Button ID="Button1" runat="server" Text="guess" OnClick="Button1_Click"/>
  
  
  
  List<int> num = new List<int>();
          protected void Button1_Click(object sender, EventArgs e)
          {
              var num1 = (List<int>)Session["num"];
              if (num1 == null)
              {
                  if (Convert.ToInt32(TextBox1.Text) == 5)
                  {
                      Response.Write("you guessed right");
                      TextBox1.Text = string.Empty;
                  }
                  else
                  {
                      Response.Write("You guessed wrong, please re-enter");
                      num.Add(Convert.ToInt32(TextBox1.Text));
                      Session["num"] = num;
                      TextBox1.Text = string.Empty;
                  }
              }
              else
              {
                  if (num1.Contains(Convert.ToInt32(TextBox1.Text)))
                  {
                      Response.Write("You enter the same number, please re-enter");
                      TextBox1.Text = string.Empty;
                  }
                  else
                  {
                      if (Convert.ToInt32(TextBox1.Text) == 5)
                      {
                          Response.Write("you guessed right");
                          TextBox1.Text = string.Empty;
                      }
                      else
                      {
                          Response.Write("You guessed wrong, please re-enter");
                          var a = (List<int>)Session["num"];
                          a.Add(Convert.ToInt32(TextBox1.Text));
                          Session["num"] = a;
                          TextBox1.Text = string.Empty;
                      }
                  }
              }
          }

  

  Best regards,

  Sam

  .NET forums are moving to a new home on Microsoft Q&A, we encourage you to go to Microsoft Q&A for .NET for posting new questions and get involved today.
• • Reply
  RawShed

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  Re: How do I prevent the same number from being entered in C# Form Textbox

  Apr 27, 2020 08:00 AM|RawShed|LINK

  static List<int> enteredNumbers = new List<int>();
  

  
  input = Int32.Parse(textBoxNumber.Text); //try-catch ile kullanmak daha mantıklı.
  if(enteredNumbers.Contains(input))
  {
      MessageBox.Show("Duplicate!");
  }
  else
  {
      enteredNumbers.Add(input);
  }

  I did my job with these codes thanks for your help
  
  

• • Reply
  PaulTheSmith

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  1620 Points

  927 Posts

  Re: How do I prevent the same number from being entered in C# Form Textbox

  Apr 27, 2020 08:04 AM|PaulTheSmith|LINK

  RawShed

  I entered the number 1 in the textbox first, how can I prevent entering the number 1 again?

  What if the '1' that they enter is the start of the number '17'?  Do you want to stop that?  I don't understand what the question means.  What do you want to happen?

  1) The user enters '1' and clicks OK

  2) Your program tells them the number is wrong

  3) The user enters '1' and clicks OK

  4) What do you want to happen?  They have already typed the number, you can't prevent them.  Do you want to disable the '1' key on the keyboard?????  Do you want to disable the 'OK' button if the input box holds a number they have already typed?  What if they typed it 5 minutes ago, now they have no idea why they can't click 'OK'

  Can you explain what it means to 'prevent entering the number 1 again'.  Why would that be anything but frustrating for the user?