C#：如何获取字符串的第一个字符？

Question

可以通过执行以下操作来检索字符串的第一个char吗？

MyString.ToCharArray[0]

Answer 1

Just MyString[0] . This uses the String.Chars indexer.

Answer 2

Mystring[0]应该就够了

Answer 3

试试这个，

string s1="good"; string s=s1.Substring(0,1);

Answer 4

You can use LINQ

char c = mystring.FirstOrDefault()

It will be equal to '\\0' if the string is empty.

Answer 5

The difference between MyString[0] and MyString.ToCharArray()[0] is that the former treats the string as a read-only array, while ToCharArray() creates a new array. The former will be quicker (along with easier) for almost anything where it will work, but ToCharArray can be necessary if you have a method that needs to accept an array, or if you want to change the array.

If the string isn't known to be non-null and non-empty you could do:

string.IsNullOrEmpty(MyString) ? (char?)null : MyString[0]

which returns a char? of either null or the first character in the string, as appropriate.

Answer 6

或者你可以这样做：

MyString[0];

Answer 7

Just another approach:

string mystr = "hello";
MessageBox.show(mystr.Substring(0, 1));

Answer 8

I think you are looking for this MyString.ToCharArray()[0]

:)

But you can use MyString[0] too.

Answer 9

Starting with C# 8.0+ we can use the range indexer syntax.

The following code:

var name = "Dotnet".Substring(0, 1)

can be written using range syntax:

var name = "Dotnet"[..1]

Try it out in Dotnet fiddle

See official docs for more examples

The above code will throw if the input string is less than range index. This LINQ will prevent that problem:

var name = "Dotnet".Take(1).ToArray()

Try it out in Dotnet fiddle

Answer 10

以下从字符串中获取第一个字符的示例可能对某人有所帮助

string anyNameForString = "" + stringVariableName[0];

Answer 11

In C# 8 you can use ranges.

myString[0..Math.Min(myString.Length, 1)]

Add a ? after myString to handle null strings.

Answer 12

MyString.Remove(1, 2); also works

Answer 13

Answer to your question is NO.

Correct is MyString[position of character]. For your case MyString[0], 0 is the FIRST character of any string.

A character value is designated with ' (single quote), like this x character value is written as 'x'.

A string value is designated with " ( double quote), like this x string value is written as "x".

So Substring() method is also does not return a character, Substring() method returns a string!!!

A string is an array of characters, and last character must be '\\0' (null) character. Thats the difference between character array and string ( which is an array of characters with last character as "end of string marker" '\\0' null.

And also notice that 'x' IS NOT EQUAL to "x". Because "x" is actually 'x'+'\\0'.

Answer 14

Maybe this will help. I'm using txtModel_Leave event then create method to detect the first char in main textbox.

private void txtMain_Leave(object sender, EventArgs e)
{
    detectFirstChar();
}

private void detectFirstChar() 
{
    string mystr = txtModel.Text;

    if (String.IsNullOrEmpty(txtModel.Text))
    {
        txtAwalan.Text = "";
    }
    else if (mystr.Substring(0, 1) == "F")
    {
        txtKategori.Text = "Finishing";               
    }
    else if((mystr.Substring(0, 1) == "H"))
    {
        txtKategori.Text = "Half";
    }
    else
    {
        txtKategori.Text = "NONE";
    }
}

Answer 15

getting a char from a string may depend on the enconding (string default is UTF-16)

https://stackoverflow.com/a/32141891

string str = new String(new char[] { '\uD800', '\uDC00', 'z' });
string first = str.Substring(0, char.IsHighSurrogate(str[0]) ? 2 : 1);