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String character array

Isn't a string already a character array in c#? Why is there a explicit ToCharacterArray function? I stumbled upon this when I was looking upon ways to reverse a string and saw a few answers converting the string to a character array first before proceeding with the loop to reverse the string. I am a beginner in coding.
Sorry if this seems stupid, but I didn't get the answer by googling.

Isn't a string already a character array in c# ?
The underlying implementation is, yes.
But you are not allowed to directly access that. String is using encapsulation to be an immutable object.
The actual array is private and hidden from view. You can use an indexer (property) to read characters but you cannot change them. The indexer is read only.
So yes, you do need ToCharacterArray() for reversing and similar actions. Note that you always end up with a different string, you cannot alter the original.

Isn't a string already a character array in c# ?
No, a string is a CLASS that encapsulates a "sequential collection of characters" (see Docs). Notice it doesn't explicitly say an "Array of Char". Now, it may be true that the string class currently uses a character array to accomplish this, but that doesn't mean it ~must~ use a character array to achieve that end. This is a fundamental concept of Object Oriented Programming that combines information hiding and the idea of a "black box" that does something. It doesn't matter how the black box (class) accomplishes its task under the hood, as long is it doesn't change the public interface presented to the end user. Perhaps, in the next version of .Net, some new-fangled magical structure that is not an array of characters will be used to implement the string class. The end user may not be aware that this change has even occurred because they can still use the string class in the same way, and if they so desire, could still output the characters to an array with ToCharArray()...even though internally the string is no longer an array of characters.

Yes String type is a character array but string array is not an character array you must have to convert each string in your array in char type so that you can easily reverse its indexes and then convert it into temporary string and then add that string to array to be reversed

Internally, the text is stored as a sequential read-only collection of Char objects.
See Programming Guide Docs

Console.WriteLine(StringHelper.ReverseString("framework"));
Console.WriteLine(StringHelper.ReverseString("samuel"));
Console.WriteLine(StringHelper.ReverseString("example string"));
OR
public static string ReverseString(string s)
{
char[] arr = s.ToCharArray();
Array.Reverse(arr);
return new string(arr);
}

C# Convert int to string and use in a Label

I have the following scenario.I am using App.config in Winforms and I have a value that is set to int (In settings). I want to use this value as a label text.
Am I correct that labels can only display string values?
This is what I have done here but not getting expected result (value to the label):
int ExclRate = Properties.Settings.Default.PriorExclTimer;
string ExclTime = ExclRate.ToString();
ExclTime = label60.Text;
PriorExclTimer is the type of the value in app.config.
I can make this work if I set the value in app.config to string, but that means I would have to convert from string to int in a much more sensitive part of the program, and I would rather not have to do that if possible. This is that line that works:
label60.Text = Properties.Settings.Default.PriorExclTimer;
I'm very new to C#, so I am really feeling my way around. Thanks...

In C# you cannot directly assign int to string. It has to always undergo conversion (either parse string to integer, or get a string out of integer).
As you say it's better to convert integer to a string for display purposes. Labels cannot directly show integer, so you will always need to convert it, or write some wrapper class if it's not enough.
Be aware that ToString() is culture specific, i.e. it will use the culture from the current thread. It might or might not be what you want. If you want InvariantCulture you can use ToString(CultureInfo.InvariantCulture).
P.S. As mentioned in the comments you can do various tricks like ExclRate + "", or in C#6 ${ExclRate}, but they are all basically converting an integer to string. I guess they all call ToString() inside.

int ExclRate = Properties.Settings.Default.PriorExclTimer;
label60.Text = ExclRate.ToString();
Code above will give you exception if PriorExclTimer is null or empty. So better you use int.TryParse to assign it to int. Not in this case, but ToString does not handle the null case, it gives exception. So you should try Convert.ToString instead.
While doing string manipulations you have to take care of culture and case (string case sensitive or insensitive)

This works for me:
int ExclRate = Properties.Settings.Default.PriorExclTimer;
label60.Text = ExclRate.ToString();
Many thanks for the insights on this topic. I will be manipulating data to and from a string a good bit for the project I am working on...

Converting Byte[] to string to remain the original byte format

I have large amount of data which consists of tables,font,bold,size,etc. Those data will be stored as byte[] in Database.
when i retrieve those data i need to convert byte[] into string,because i need to some find & replace from this string,after i convert this string into byte[],am losing the original data structure which means, i can't able to see any tables,font,bold etc. properly. So how can i find and replace in byte[] by converting string and also to keep remain the data in original format.

The short answer is don't. Figure out the format of the data and see what you can do to do the manipulation. If the data is actually text, just stored as byte[], your approach would work, provided you encode the string correctly (ie. if your DB expects UTF-8, use UTF-8 encoding, if it's windows-1251, use that).
If you have a structure where a part of it is a string, what you're doing can't really work well. First, you probably want to modify just the relevant parts of the field. On MS SQL, you have handy functions for that. But even then, you should know what's actually stored there, not just assume that a string replace will magically work.
Now, a hack could be to use an explicit encoding that doesn't break the non-string data. That would be some single-byte encoding that doesn't do anything fancy. This is OK as long as you use the same encoding while reading the text data - however, if you use any variant of unicode, you're out of luck; due to features like string normalization, you can't really guarantee that what comes in comes out the same way, per-byte. It's generally a bad practice anyway.
Don't forget that it's quite possible the string you are looking for is actually somewhere outside of the text fields - even by pure chance, it can happen, and certain practices make that even more likely.
Again: figure out the data format inside that data field - then you can decide how to do what you want.

Try this
string result = System.Text.Encoding.UTF8.GetString(byteArray)

To make Byte[] to String
byte[] byteArray = new byte[10]; // put your byte array here
public void byteToString()
{
stringTemp = "";
stringTemp = BitConverter.ToString(byteArray).Replace("-", "");
}
And your data still in byteArray.. :)

If the byte Array contains binary data and is no string, try to convert it to base64:
Convert.ToBase64String(yourByteArray);

Replace control character in string c#

Some text fields in my database have bad control characters embedded. I only noticed this when trying to serialize an object and get an xml error on char  and . There are probably others.
How do I replace them using C#? I thought something like this would work:
text.Replace('\x2', ' ');
but it doesn't.
Any help appreciated.

Strings are immutable - you need to reassign:
text = text.Replace('\x2', ' ');

exactly as was said above, strings are immutable in C#. This means that the statement:
text.Replace('\x2', ' ');
returned the string you wanted,but didn't change the string you gave it. Since you didn't assign the return value anywhere, it was lost. That's why the statement above should fix the problem:
text = text.Replace('\x2', ' ');
If you have a string that you are frequently making changes to, you might look at the StringBuilder object, which works very much like regular strings, but they are mutable, and therefore much more efficient in some situatations.
Good luck!
-Craig

The larger problem you're dealing with is the XmlSerialization round trip problem. You start with a string, you serialize it to xml, and then you deserialize the xml to a string. One expects that this always results in a string that is equivalent to the first string, but if the string contains control characters, the deserialization throws an exception.
You can fix that by passing an XmlTextReader instead of a StreamReader to the Deserialize method. Set the XmlTextReader's Normalization property to false.
You should also be able to solve this problem by serializing the string as CDATA; see How do you serialize a string as CDATA using XmlSerializer? for more information.

state at compile time not known

I need a way to Parse an string into an integer value in c#. The problem is the user chosses a string from a combo box which contains strings such as "AAAAA" or "5". That means only at run time it is known if the parameter is a real string or an string which can be parsed to an integer. I tried around with reflection and have the fitting Parameter object.
ParameterInfo p = ps[i];
Type t = p.ParameterType;
I don't know how to go on from there or if it even is possible. I can't use if else statments because the program is supposed to load other interfaces with new parameters as well. So I could handle the default ones with if else statmentes but when a new interface with new Methodinfos is loaded that dos not work anymore.

I'm not usre that understood all your constraints. However you can parse string by using Int32.TryParse in case target string is not necessarily valid.

Int32.TryParse whould help you with that

To parse a string into an integer, you can use Convert.ToInt32(string_var), or any of the other conversion methods. See here for more.