First Character of String Lowercase - C#

This will work:

string s = "ConfigService";

if (s != string.Empty && char.IsUpper(s[0]))
{
    s =  char.ToLower(s[0]) + s.Substring(1);
}

Console.WriteLine(s);  

One way:

string newString = oldString;
if (!String.IsNullOrEmpty(newString))
    newString = Char.ToLower(newString[0]) + newString.Substring(1);

For what it's worth, an extension method:

public static string ToLowerFirstChar(this string input)
{
    if(string.IsNullOrEmpty(input))
        return input;

    return char.ToLower(input[0]) + input.Substring(1);
}

Usage:

string newString = "ConfigService".ToLowerFirstChar(); // configService

You could try this:

lower = source.Substring(0, 1).ToLower() + source.Substring(1);