How can I get just the first ten characters of a string in C# [duplicate]
I have a string and I need to get just the first ten characters. Is there a way that I can do this easily.
I hope someone can show me.
You can use the String.Substring method; e.g.:
string s = "Lots and lots of characters";
string firstTen = s.Substring(0, 10);
You could create an extension method, like this:
public static class Extension
{
public static string Left(this String input, int length)
{
return (input.Length < length) ? input : input.Substring(0, length);
}
}
and then call it like this:
string something = "I am a string... truncate me!";
something.Left(10);
Depends :-)
Normally you are probably looking for SubString... but if you're doing fancy stuff with unicode, this demonstrates where that will go wrong (e.g. unicode ranges > 0xFFFF):
static void Main(string[] arg)
{
string ch = "(\xd808\xdd00汉语 or 漢語, Hànyǔ)";
Console.WriteLine(ch.Substring(0, Math.Min(ch.Length, 10)));
var enc = Encoding.UTF32.GetBytes(ch);
string first10chars = Encoding.UTF32.GetString(enc, 0, Math.Min(enc.Length, 4 * 10));
Console.WriteLine(first10chars);
Console.ReadLine();
}
The reason that goes wrong is because chars are 16-bit and Length checks UTF-16 chars and not unicode characters. That said, that's probably not your scenario.
A quick, one-liner where the variable s is your string:
public string GetFirstTenCharacters(string s)
{
// This says "If string s is less than 10 characters, return s.
// Otherwise, return the first 10 characters of s."
return (s.Length < 10) ? s : s.Substring(0, 10);
}
And just call this method like this:
string result = this.GetFirstTenCharacters("Hello, this is a string!");
there will be no exception even if string lengeth is <10
String s = "characters";
String firstTen = s.Substring(0, (s.Length < 10) ? s.Length : 10);
string longStr = "A lot of characters";
string shortStr = new string(longStr.Take(10).ToArray());
Lots of options like:
string original = "A string that will only contain 10 characters";
//first option
string test = original.Substring(0, 10);
//second option
string AnotherTest = original.Remove(10);
//third option
string SomeOtherTest = string.Concat(original.Take(10));
Hope it helps out.
Getting the substring of specific length is very simple and easy in C#, however it's important to get it done in the most efficient way.
Points to be considered:
- Error Handling
- Performance
Below is an example of performing it in the simplest and most efficient way possible:
ASPX:
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox runat="server" ID="txtInput"></asp:TextBox>
<asp:Button runat="server" ID="btn10Chars" onclick="btn10Chars_Click" text="show 10 Chars of string"/><br />
<asp:Label runat ="server" ID="lblOutput"></asp:Label>
</div>
</form>
C#:
public partial class Home : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btn10Chars_Click(object sender, EventArgs e)
{
lblOutput.Text = txtInput.Text.Length > 10 ? txtInput.Text.Substring(0, 10) : txtInput.Text + " : length is less than 10 chars...";
}
}
Take-aways from the example:
- Error Handling without using try catch.
- Ternary operator is used which is best in terms of performance while compared to if condition.
- All together, it's just one line of code to achieve the required functionality.
It depends on what you mean by character. The C# char type is a WORD (or a ushort - min value: 0 and max value: 65535 (2^16)). Different text normalization might yield different results, example: NFC might represent a character as 1 char while NFD would represent that same character as 2.
Using String.Substring should work if you're only using 7-bit ASCII. Text normalization will play a role in 8-bit/extended ASCII, UTF-8 ~ 32 due to surrogate pairs and combining characters.
If you want to grab the first 10 characters (not char's), you should use:
public static string TakeCharacters(string input, int index, int count)
{
if (input == null) return null;
if (index >= input.Length)
throw new ArgumentOutOfRangeException(
"index",
string.Format("index {0} is out of range (max {1})", index, input.Length - 1));
if (count <= 0)
throw new ArgumentException("length should be greater than zero", "count");
var builder = new StringBuilder();
while (index < input.Length && count > 0)
{
var c = StringInfo.GetNextTextElement(input, index);
builder.Append(c);
index += c.Length;
count--;
}
return builder.ToString();
}
Note that StringInfo combines characters/pairs and GetNextTextElement returns a string. The index and count parameters are passed by value and thus can be used inside the method without aliasing.
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