Convert all first letter to upper case, rest lower for each word

string s = "THIS IS MY TEXT RIGHT NOW";

s = System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(s.ToLower());

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I probably prefer to invoke the ToTitleCase from CultureInfo (System.Globalization) than Thread.CurrentThread (System.Threading):

string s = "THIS IS MY TEXT RIGHT NOW";
s = CultureInfo.CurrentCulture.TextInfo.ToTitleCase(s.ToLower());

But it should be the same as jspcal's solution.

EDIT

Actually, those solutions are not the same: CurrentThread --calls--> CultureInfo!

System.Threading.Thread.CurrentThread.CurrentCulture

string s = "THIS IS MY TEXT RIGHT NOW";
s = System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(s.ToLower());

IL_0000:  ldstr       "THIS IS MY TEXT RIGHT NOW"
IL_0005:  stloc.0     // s
IL_0006:  call        System.Threading.Thread.get_CurrentThread
IL_000B:  callvirt    System.Threading.Thread.get_CurrentCulture
IL_0010:  callvirt    System.Globalization.CultureInfo.get_TextInfo
IL_0015:  ldloc.0     // s
IL_0016:  callvirt    System.String.ToLower
IL_001B:  callvirt    System.Globalization.TextInfo.ToTitleCase
IL_0020:  stloc.0     // s

System.Globalization.CultureInfo.CurrentCulture

string s = "THIS IS MY TEXT RIGHT NOW";
s = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(s.ToLower());

IL_0000:  ldstr       "THIS IS MY TEXT RIGHT NOW"
IL_0005:  stloc.0     // s
IL_0006:  call        System.Globalization.CultureInfo.get_CurrentCulture
IL_000B:  callvirt    System.Globalization.CultureInfo.get_TextInfo
IL_0010:  ldloc.0     // s
IL_0011:  callvirt    System.String.ToLower
IL_0016:  callvirt    System.Globalization.TextInfo.ToTitleCase
IL_001B:  stloc.0     // s

References:

CultureInfo Class

Thread.CurrentCulture Property

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There are a couple of ways to go about converting the first character of a string to upper case.

The first way is to create a method that simply caps the first character and appends the rest of the string using a substring:

public string UppercaseFirst(string s)
{
    return char.ToUpper(s[0]) + s.Substring(1);
}

The second way (which is slightly faster) is to split the string into a character array and then rebuild the string:

public string UppercaseFirst(string s)
{
    char[] a = s.ToCharArray();
    a[0] = char.ToUpper(a[0]);
    return new string(a);
}

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If you're using on a web page, you can also use CSS:

style="text-transform:capitalize;"

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Untested but something like this should work:

var phrase = "THIS IS MY TEXT RIGHT NOW";
var rx = new System.Text.RegularExpressions.Regex(@"(?<=\w)\w");
var newString = rx.Replace(phrase,new MatchEvaluator(m=>m.Value.ToLowerInvariant()));

Essentially it says "preform a regex match on all occurrences of an alphanumeric character that follows another alphanumeric character and then replace it with a lowercase version of itself"

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When building big tables, speed is a concern so Jamie Dixon's second function is best, but it doesn't completely work as is...

It fails to take all of the letters to lowercase, and it only capitalizes the first letter of the string, not the first letter of each word in the string... the below option fixes both issues:

    public string UppercaseFirstEach(string s)
    {
        char[] a = s.ToLower().ToCharArray();

        for (int i = 0; i < a.Count(); i++ )
        {
            a[i] = i == 0 || a[i-1] == ' ' ? char.ToUpper(a[i]) : a[i];

        }

        return new string(a);
    }

Although at this point, whether this is still the fastest option is uncertain. The Regex solution provided by George Mauer might be faster... someone who cares enough should test it.

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I don't know if the solution below is more or less efficient than jspcal's answer, but I'm pretty sure it requires less object creation than Jamie's and George's.

string s = "THIS IS MY TEXT RIGHT NOW";
StringBuilder sb = new StringBuilder(s.Length);
bool capitalize = true;
foreach (char c in s) {
    sb.Append(capitalize ? Char.ToUpper(c) : Char.ToLower(c));
    capitalize = !Char.IsLetter(c);
}
return sb.ToString();

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Try this technique; It returns the desired result

CultureInfo.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());

And don't forget to use System.Globalization.

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In addition to the first answer, remember to change string selectionstart index to the end of the word or you will get the reverse order of letters in the string.

s.SelectionStart = s.Length;

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This is one of the possible solutions you might be interested in. Traversing an array of characters from right to left and vice versa in one loop.

public static string WordsToCapitalLetter(string value)
{
    if (string.IsNullOrWhiteSpace(value))
    {
        throw new ArgumentException("value");
    }

    int inputValueCharLength = value.Length;
    var valueAsCharArray = value.ToCharArray();

    int min = 0;
    int max = inputValueCharLength - 1;

    while (max > min)
    {
        char left = value[min];
        char previousLeft = (min == 0) ? left : value[min - 1];

        char right = value[max];
        char nextRight = (max == inputValueCharLength - 1) ? right : value[max - 1];

        if (char.IsLetter(left) && !char.IsUpper(left) && char.IsWhiteSpace(previousLeft))
        {
            valueAsCharArray[min] = char.ToUpper(left);
        }

        if (char.IsLetter(right) && !char.IsUpper(right) && char.IsWhiteSpace(nextRight))
        {
            valueAsCharArray[max] = char.ToUpper(right);
        }

        min++;
        max--;
    }

    return new string(valueAsCharArray);
}

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jspcal's answer as a string extension.

File Program.cs

class Program
{
    static void Main(string[] args)
    {
        var myText = "MYTEXT";
        Console.WriteLine(myText.ToTitleCase()); //Mytext
    }
}

File StringExtensions.cs

using System;
public static class StringExtensions
{

    public static string ToTitleCase(this string str)
    {
        if (str == null)
            return null;

        return System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());
    }
}

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