Getting input from textbox as "console"

Question

Hi all. I am learning C# and have a Windows forms project that I am working on to learn various techniques. Basically it has a text box that I use to mimic a console. The user enters a command followed by the Enter key and the program reads that in and interprets
it. I also have some rudimentary "batch" commands, such as IF/THEN, INPUT and PRINT.
The application has two main components: The form and a class. The form takes care of interpreting the commands that the user enters and the class implements the three batch commands (more to follow in the near future). The issue that I am having is that
sometimes (maybe 2%) the INPUT functionality does not work. When I enter a string and press Enter an empty string is returned. I have tried to debug this as much as I can, but it is difficult since this problem only happens once in a while.
I have extracted the INPUT functionality and duplicated it in a simple app which I present here. The test app contains one button called btnConRead and a multi line text box called txtConsole. Clicking the button "forces" the app into "run"
mode where the batch commands are interpreted. For this example I run the code that runs when an INPUT command is being processed. The app prompts with "OK" and waits for the user to type something in. When the user presses the Enter key the entered
string is echoed on the console. The form module contains this code:
string sKBBuf = ""; //App wide KB buffer when form Key preview is enabled.
bool bEnter;
private delegate void DisplayMsgDelegate(string sMsg);
private void cEventPrint(object sender, PrintDataEventArgs e)
Display(txtConsole, e.sPrintLine);
private void cEventRead(object sender, ReadDataEventArgs e)
//Event that reads text from the console and returns it.
//This event requires input from the user. It traps the program here until the user
//presses Enter.
//Clear the KB buffer.
sKBBuf = "";
//Loop incessantly until user presses Enter key or Stop key (s).
do
//Braindead.
} while (!bEnter);
if (bEnter)
//User pressed the Enter key, return the KB buffer.
e.sReadLine = sKBBuf;
//Empty buffer.
sKBBuf = "";
//Reset Enter key flag.
bEnter = false;
//Push CRLF to console.
Display(txtConsole, Environment.NewLine);
private void DisplayMsg(string sMsg)
txtConsole.AppendText(sMsg);
private void Display(TextBox txtOutput, string sMsg, bool bToCon = true)
//Check output to console flag.
if (bToCon)
if (txtOutput.InvokeRequired)
txtOutput.Invoke(new DisplayMsgDelegate(DisplayMsg), sMsg);
else
txtOutput.AppendText(sMsg);
private void GetConInput()
clsExample cEx = new clsExample();
cEx.ReadData += cEventRead;
cEx.PrintData += cEventPrint;
System.Threading.Thread runThread = new System.Threading.Thread(() =>
cEx.Process();
this.KeyPreview = false;
this.KeyPreview = true;
runThread.Start();
private void btnReadCon_Click(object sender, EventArgs e)
//Prep stuff
sKBBuf = "";
txtConsole.Focus();
Display(txtConsole, "OK" + Environment.NewLine);
//Read console textbox
GetConInput();
private void Form1_KeyPress(object sender, KeyPressEventArgs e)
bEnter = e.KeyChar == 13;
//Save to buffer. At this time I am not distinguishing from letter or digits.
//But I do need to check for a BS.
if (e.KeyChar == 8)
//Yeah, BS, remove the last char, if any.
if (sKBBuf.Length > 0)
sKBBuf = sKBBuf.Substring(0, sKBBuf.Length - 1);
else
sKBBuf += e.KeyChar;
The class is called clsExample and contains the following code:
//Event raised when data needs to be printed to console.
public event EventHandler<PrintDataEventArgs> PrintData;
//Event raised when data needs to be read from console.
public event EventHandler<ReadDataEventArgs> ReadData;
protected virtual void OnReadData(ReadDataEventArgs e)
EventHandler<ReadDataEventArgs> handler = ReadData;
if (handler != null)
handler(this, e);
protected virtual void OnPrintData(PrintDataEventArgs e)
EventHandler<PrintDataEventArgs> handler = PrintData;
if (handler != null)
handler(this, e);
public void Process()
ReadDataEventArgs argsRead = new ReadDataEventArgs();
PrintDataEventArgs args = new PrintDataEventArgs();
string sMsg = "";
//Get input from user.
OnReadData(argsRead);
if (argsRead.sReadLine.Length > 0)
//I have something
sMsg = argsRead.sReadLine;
else
//No data
sMsg = "*";
args.sPrintLine = sMsg + Environment.NewLine;
OnPrintData(args);
Plus two more support classes for the Print and Read events:
public class PrintDataEventArgs : EventArgs
public string sPrintLine { get; set; }
public class ReadDataEventArgs : EventArgs
public string sReadLine { get; set; }
 All the above was necessary so that the Process procedure running in a different thread could interact with the UI elements in the main form. The above mostly works, but I wonder if I am doing it the right way. I don't particularly like the use of
global flags, such as bEnter or having empty loops to just "kill" time, such as the one found in the cEventRead procedure.
In the cEventRead procedure I had the if() block immediately following the empty loop inside
the loop and moved it out of there to see if this made any difference, but apparently it did not. Can anyone provide any feedback or suggestions of what I could change to make it work 100% of the time? I appreciate your time and effort. Thank you, Saga
You can't take the sky from me

Answer 1

Hi all. I am learning C# and have a Windows forms project that I am working on to learn various techniques. Basically it has a text box that I use to mimic a console. The user enters a command followed by the Enter key and the program reads that in and interprets
it. I also have some rudimentary "batch" commands, such as IF/THEN, INPUT and PRINT.
//Loop incessantly until user presses Enter key or Stop key (s).
do
//Braindead.
} while (!bEnter);
Hi Saga,
Please don't use such kind of loop in your code, if you want to monitor the user input, just use the KeyPress event provided by the TextBox control.
Control.KeyPress
Event
If you just want to execute some standard commands, I recommend that you use
Process to start cmd.exe to execute the command, for example:
void ExecuteCommand(string command)
int exitCode;
ProcessStartInfo processInfo;
Process process;
processInfo = new ProcessStartInfo("cmd.exe", "/c " + command);
processInfo.CreateNoWindow = true;
processInfo.UseShellExecute = false;
// *** Redirect the output ***
processInfo.RedirectStandardError = true;
processInfo.RedirectStandardOutput = true;
process = Process.Start(processInfo);
process.WaitForExit();
// *** Read the streams ***
string output = process.StandardOutput.ReadToEnd();
string error = process.StandardError.ReadToEnd();
exitCode = process.ExitCode;
Console.WriteLine("output>>" + (String.IsNullOrEmpty(output) ? "(none)" : output));
Console.WriteLine("error>>" + (String.IsNullOrEmpty(error) ? "(none)" : error));
Console.WriteLine("ExitCode: " + exitCode.ToString(), "ExecuteCommand");
process.Close();
If it's powershell script, you can also use the existing library to execute it, check this blogpost:
Executing PowerShell scripts from C#
We are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time. Thanks for helping make community forums a great place.
Click
HERE to participate the survey.