C# 如何在.Net控制台应用程序中设置默认输入值?
如何在.net控制台应用程序中设置默认输入值 以下是一些虚构的代码:C# 如何在.Net控制台应用程序中设置默认输入值?,c#,.net,input,console,console-application,C#,.net,Input,Console,Console Application,如何在.net控制台应用程序中设置默认输入值 以下是一些虚构的代码: Console.Write("Enter weekly cost: "); string input = Console.ReadLine("135"); // 135 is the default. The user can change or press enter to accept decimal weeklyCost = decimal.Parse(input); 当然,我不
Console.Write("Enter weekly cost: ");
string input = Console.ReadLine("135"); // 135 is the default. The user can change or press enter to accept
decimal weeklyCost = decimal.Parse(input);
当然,我不希望事情会这么简单。我打赌必须做一些低级的、不受管理的事情;我只是不知道怎么做
编辑
我知道我可以用默认值替换无输入。这不是我要问的。我试图了解实现我描述的行为所涉及的内容:为用户提供一个可编辑的默认值。我也不担心输入验证;我的问题与此无关。或者。。。只需测试输入的值,如果为空,则将默认值放入输入。简单解决方案,如果用户未输入任何内容,则指定默认值:
Console.Write("Enter weekly cost: ");
string input = Console.ReadLine();
decimal weeklyCost = String.IsNullOrEmpty(input) ? 135 : decimal.Parse(input);
在处理用户输入时,您应该预料到它可能包含错误。因此,如果用户未输入数字,可以使用TryParse以避免出现异常:
Console.Write("Enter weekly cost: ");
string input = Console.ReadLine();
decimal weeklyCost;
if ( !Decimal.TryParse(input, out weeklyCost) )
weeklyCost = 135;
这将被视为处理用户输入的最佳实践。如果您需要解析许多用户输入,请使用helper函数。一种方法是使用具有null的方法,如果解析失败,则返回null。然后,使用以下命令很容易指定默认值:
然后,读取输入并指定默认值非常简单:
decimal d = SafeConvert.ToDecimal(Console.ReadLine()) ?? 135;
可以使用以下帮助器方法:
public static string ReadWithDefaults(string defaultValue)
{
string str = Console.ReadLine();
return String.IsNullOrEmpty(str) ? defaultValue : str;
}
我相信,您可以通过聆听每个按键来手动管理: 快速组合示例:
// write the initial buffer
char[] buffer = "Initial text".ToCharArray();
Console.WriteLine(buffer);
// ensure the cursor starts off on the line of the text by moving it up one line
Console.SetCursorPosition(Console.CursorLeft + buffer.Length, Console.CursorTop - 1);
// process the key presses in a loop until the user presses enter
// (this might need to be a bit more sophisticated - what about escape?)
ConsoleKeyInfo keyInfo = Console.ReadKey(true);
while (keyInfo.Key != ConsoleKey.Enter)
{
switch (keyInfo.Key)
{
case ConsoleKey.LeftArrow:
...
// process the left key by moving the cursor position
// need to keep track of the position in the buffer
// if the user presses another key then update the text in our buffer
// and draw the character on the screen
// there are lots of cases that would need to be processed (backspace, delete etc)
}
keyInfo = Console.ReadKey(true);
}
这相当复杂-您必须确保光标不超出范围,并手动更新缓冲区。这里有一个简单的解决方案:
public static string ConsoleReadLineWithDefault(string defaultValue)
{
System.Windows.Forms.SendKeys.SendWait(defaultValue);
return Console.ReadLine();
}
然而,它并不完整。SendWait输入字符串中的某些字符具有特殊含义,因此必须对其进行转义(例如+,(,)等)
有关完整的说明,请参阅
我继续并完成了Matt的实施方法:
public static string ReadInputWithDefault(string defaultValue, string caret = "> ")
{
Console.WriteLine(); // make sure we're on a fresh line
List<char> buffer = defaultValue.ToCharArray().Take(Console.WindowWidth - caret.Length - 1).ToList();
Console.Write(caret);
Console.Write(buffer.ToArray());
Console.SetCursorPosition(Console.CursorLeft, Console.CursorTop);
ConsoleKeyInfo keyInfo = Console.ReadKey(true);
while (keyInfo.Key != ConsoleKey.Enter)
{
switch (keyInfo.Key)
{
case ConsoleKey.LeftArrow:
Console.SetCursorPosition(Math.Max(Console.CursorLeft - 1, caret.Length), Console.CursorTop);
break;
case ConsoleKey.RightArrow:
Console.SetCursorPosition(Math.Min(Console.CursorLeft + 1, caret.Length + buffer.Count), Console.CursorTop);
break;
case ConsoleKey.Home:
Console.SetCursorPosition(caret.Length, Console.CursorTop);
break;
case ConsoleKey.End:
Console.SetCursorPosition(caret.Length + buffer.Count, Console.CursorTop);
break;
case ConsoleKey.Backspace:
if (Console.CursorLeft <= caret.Length)
{
break;
}
var cursorColumnAfterBackspace = Math.Max(Console.CursorLeft - 1, caret.Length);
buffer.RemoveAt(Console.CursorLeft - caret.Length - 1);
RewriteLine(caret, buffer);
Console.SetCursorPosition(cursorColumnAfterBackspace, Console.CursorTop);
break;
case ConsoleKey.Delete:
if (Console.CursorLeft >= caret.Length + buffer.Count)
{
break;
}
var cursorColumnAfterDelete = Console.CursorLeft;
buffer.RemoveAt(Console.CursorLeft - caret.Length);
RewriteLine(caret, buffer);
Console.SetCursorPosition(cursorColumnAfterDelete, Console.CursorTop);
break;
default:
var character = keyInfo.KeyChar;
if (character < 32) // not a printable chars
break;
var cursorAfterNewChar = Console.CursorLeft + 1;
if (cursorAfterNewChar > Console.WindowWidth || caret.Length + buffer.Count >= Console.WindowWidth - 1)
{
break; // currently only one line of input is supported
}
buffer.Insert(Console.CursorLeft - caret.Length, character);
RewriteLine(caret, buffer);
Console.SetCursorPosition(cursorAfterNewChar, Console.CursorTop);
break;
}
keyInfo = Console.ReadKey(true);
}
Console.Write(Environment.NewLine);
return new string(buffer.ToArray());
}
private static void RewriteLine(string caret, List<char> buffer)
{
Console.SetCursorPosition(0, Console.CursorTop);
Console.Write(new string(' ', Console.WindowWidth - 1));
Console.SetCursorPosition(0, Console.CursorTop);
Console.Write(caret);
Console.Write(buffer.ToArray());
}
公共静态字符串ReadInputWithDefault(字符串defaultValue,字符串插入符号=“>”)
{
Console.WriteLine();//请确保我们有新的线索
List buffer=defaultValue.ToCharArray().Take(Console.WindowWidth-caret.Length-1.ToList();
Console.Write(插入符号);
Console.Write(buffer.ToArray());
Console.SetCursorPosition(Console.CursorLeft,Console.CursorTop);
ConsoleKeyInfo-keyInfo=Console.ReadKey(true);
while(keyInfo.Key!=ConsoleKey.Enter)
{
开关(keyInfo.Key)
{
case ConsoleKey.LeftArrow:
SetCursorPosition(Math.Max(Console.CursorLeft-1,插入符号.Length),Console.CursorTop);
打破
case ConsoleKey.RightArrow:
SetCursorPosition(Math.Min(Console.CursorLeft+1,插入符号.Length+buffer.Count),Console.CursorTop);
打破
case ConsoleKey.主页:
Console.SetCursorPosition(插入符号长度,Console.CursorTop);
打破
案例控制台。结束:
Console.SetCursorPosition(插入符号长度+缓冲区计数,Console.CursorTop);
打破
案例控制台键。退格:
if(Console.CursorLeft=caret.Length+buffer.Count)
{
打破
}
var cursorcolumnferdelete=Console.CursorLeft;
buffer.removet(Console.CursorLeft-caret.Length);
重写行(插入符号、缓冲区);
Console.SetCursorPosition(cursorColumnAfterDelete,Console.CursorTop);
打破
违约:
var character=keyInfo.KeyChar;
if(character<32)//不是可打印的字符
打破
var cursorAfterNewChar=Console.CursorLeft+1;
if(cursorAfterNewChar>Console.WindowWidth | |插入符号长度+缓冲区计数>=Console.WindowWidth-1)
{
break;//当前只支持一行输入
}
插入(Console.CursorLeft-caret.Length,character);
重写行(插入符号、缓冲区);
Console.SetCursorPosition(cursorAfterNewChar,Console.CursorTop);
打破
}
keyInfo=Console.ReadKey(true);
}
Console.Write(Environment.NewLine);
返回新字符串(buffer.ToArray());
}
专用静态行(字符串插入符号、列表缓冲区)
{
Console.SetCursorPosition(0,Console.CursorTop);
Write(新字符串(“”,Console.WindowWidth-1));
Console.SetCursorPosition(0,Console.CursorTop);
Console.Write(插入符号);
Console.Write(buffer.ToArray());
}
注:
- 仅适用于一行输入
- 您可以定义可编辑文本区域前的内容(
参数)caret
- 使用风险自负,可能仍然存在一些索引自动查找问题。;)李>
- 现在有一种更好的方法,请查看nuget上的Readline:
install package Readline
var input=ReadLine.Read(“输入周成本:”,“135”)代码>
我喜欢使用控制台编写交互式测试,使用默认值确实有帮助。您将他的虚拟参数保留在了
中。您可以按照建议的答案对其进行编码-用户不会关心编码技术。对于理论上的问题,如果有一种方法可以用readline实现的话——可能没有(至少没有记录在案)。但是——我知道,如果你想这么做,我们正在寻找一种方法ReadLine
string _weeklycost = ""; Console.WriteLine("Enter weekly cost: "); System.Windows.Forms.SendKeys.SendWait("135"); _weeklycost = Console.ReadLine();
public static string ReadInputWithDefault(string defaultValue, string caret = "> ") { Console.WriteLine(); // make sure we're on a fresh line List<char> buffer = defaultValue.ToCharArray().Take(Console.WindowWidth - caret.Length - 1).ToList(); Console.Write(caret); Console.Write(buffer.ToArray()); Console.SetCursorPosition(Console.CursorLeft, Console.CursorTop); ConsoleKeyInfo keyInfo = Console.ReadKey(true); while (keyInfo.Key != ConsoleKey.Enter) { switch (keyInfo.Key) { case ConsoleKey.LeftArrow: Console.SetCursorPosition(Math.Max(Console.CursorLeft - 1, caret.Length), Console.CursorTop); break; case ConsoleKey.RightArrow: Console.SetCursorPosition(Math.Min(Console.CursorLeft + 1, caret.Length + buffer.Count), Console.CursorTop); break; case ConsoleKey.Home: Console.SetCursorPosition(caret.Length, Console.CursorTop); break; case ConsoleKey.End: Console.SetCursorPosition(caret.Length + buffer.Count, Console.CursorTop); break; case ConsoleKey.Backspace: if (Console.CursorLeft <= caret.Length) { break; } var cursorColumnAfterBackspace = Math.Max(Console.CursorLeft - 1, caret.Length); buffer.RemoveAt(Console.CursorLeft - caret.Length - 1); RewriteLine(caret, buffer); Console.SetCursorPosition(cursorColumnAfterBackspace, Console.CursorTop); break; case ConsoleKey.Delete: if (Console.CursorLeft >= caret.Length + buffer.Count) { break; } var cursorColumnAfterDelete = Console.CursorLeft; buffer.RemoveAt(Console.CursorLeft - caret.Length); RewriteLine(caret, buffer); Console.SetCursorPosition(cursorColumnAfterDelete, Console.CursorTop); break; default: var character = keyInfo.KeyChar; if (character < 32) // not a printable chars break; var cursorAfterNewChar = Console.CursorLeft + 1; if (cursorAfterNewChar > Console.WindowWidth || caret.Length + buffer.Count >= Console.WindowWidth - 1) { break; // currently only one line of input is supported } buffer.Insert(Console.CursorLeft - caret.Length, character); RewriteLine(caret, buffer); Console.SetCursorPosition(cursorAfterNewChar, Console.CursorTop); break; } keyInfo = Console.ReadKey(true); } Console.Write(Environment.NewLine); return new string(buffer.ToArray()); } private static void RewriteLine(string caret, List<char> buffer) { Console.SetCursorPosition(0, Console.CursorTop); Console.Write(new string(' ', Console.WindowWidth - 1)); Console.SetCursorPosition(0, Console.CursorTop); Console.Write(caret); Console.Write(buffer.ToArray()); }