字符串的正则表达式不以特殊的字符和空格开头 [英] Regular expression for string not start with special caracter and space

问题描述

我必须制作正则表达式，不允许字符串以sprecial caracter开头。

例如：

[e-mail] - 正确

@ 45gm.com - 错误



我该怎么做？



什么我试过了：



i让这个正则表达式...

string TrNo = txtConsignor.Text.ToString（） ;

TrNo = System.Text.RegularExpressions.Regex.Replace（TrNo，[^ a-zA-Z0-9 \\ t]，）;

txtConsignor.Text = TrNo.TrimStart（）;

i have to make regular expression which not allow string start with sprecial caracter.
for exampel :
[e-mail] - right
@45gm.com - wrong

how can i do this ?

What I have tried:

i have make this regular expression...
string TrNo = txtConsignor.Text.ToString();
TrNo = System.Text.RegularExpressions.Regex.Replace(TrNo, "[^a-zA-Z0-9\\s]", "");
txtConsignor.Text = TrNo.TrimStart();

推荐答案

你在做什么并不禁止特殊字符，它会删除它们。并且它也不要求它们在开始时！

因此，如果你的字符串是@ 45gm.com，那么它将它转换为45gmcom 而不是告诉任何人它已经完成了它。 因此，存储（或以其他方式处理）的内容也不是有效的电子邮件，并且在解决问题时为时已晚。更糟糕的是，它对你的正确字符串做了同样的事情：[e-mail]成为45gfcom



你需要的是用它作为一个正则表达式并检查结果：

What you are doing doesn't prohibit special characters, it removes them. And it doesn't require them to be at the start, either!
So if your string is "@45gm.com" then it converts it to 45gmcom and doesn't tell anyone it's done it. So what gets stored (or otherwise processed) isn;t a valid email either, and gives problems way on down the line, when it's too late to fix it. Worse, it does the same thing with your "correct" string: "[e-mail]" becomes "45gfcom"

What you need is to use it as a regex and check the result:

Match m = Regex.Match(trNo, "^[^a-zA-Z0-9\\s]");
if (m.Success)
    {
    ... report problem to user ...
    return;
    }

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