# String Manipulation

We are going to see some useful methods that can be used on String objects. To illustrate the methods, we can use this variable as our example:

var text = "It's a cold day in the woods";

# Substring

This method returns a brand-new string with the value: "a cold day"

var subtext = text.Substring(5, 10);
Console.WriteLine(subtext);

So, we can get only a part of a string.

# Join

We can create a new string based on an array of values and a separator.

var numbers = new[] { 1, 2, 3, 4, 5 };

var result = string.Join(",", numbers);
Console.WriteLine(result);

# Concat

We can combine two string together. If we run just this line:

string.Concat(text, " of the village");
Console.WriteLine(text);

The value of the text variable doesn't change (we know that the string is immutable). Therefore, we need to reassign the new value:

text = string.Concat(text, " of the village");
Console.WriteLine(text);

Instead of string.Concat(), we can use the plus operator + to combine strings together.

text += " of the village";
Console.WriteLine(text);

This operator is called the concatenation operator.

# Replace

We can replace any string occurance inside of a string:

text = text.Replace("cold", "warm");
Console.WriteLine(text);

This works the same as the string.Concat() method: it returns a new string. We need to reassign the value to the text variable. If not, the value of text remains the same.

Like the Substring method, Replace actually returns a new string and does not modify the original string.

# ToUpper

We can transform all the characters of a string to upper case:

text = text.ToUpper();
Console.WriteLine(text);

# ToLower

text = text.ToLower();
Console.WriteLine(text);

# Insert

We can insert another sequence inside of a string:

text = text.Insert(12, "foggy ");
Console.WriteLine(text);

# IndexOf

We can find the starting index of a specific string inside another one:

var index = text.IndexOf("warm");
Console.WriteLine(index);

# Length

We can get the length / size of a string through the Length property:

var length = text.Length;
Console.WriteLine(length);

# Contains

We can use the Contains method to check if there is a string in another one:

if (text.Contains("warm"))
{
    Console.WriteLine("The string was found");
}

# Copy

We can copy the value of one string to another one:

var anotherText = string.Copy(text);
Console.WriteLine(anotherText);

# StartsWith

This method checks whether or not a string starts with another one:

var result = text.StartsWith("It's a");
Console.Writeline(result); // True

# EndsWith

This performs in the opposite way of StartsWith:

var result = text.StartsWith("in the woods");
Console.Writeline(result); // True

# Trim

We can remove white-spaces from the beginning and end of a string with the Trim method:

var phoneNumber = " 232 323 232  ";
phoneNumber = phoneNumber.Trim();

You can change how the Trim method works by providing a set of characters:

var phoneNumber = ".232 323 232,";
var chars = new char[] { '.', ',' };
phoneNumber = phoneNumber.Trim(chars);

# ToArray

We can transform a string to an array:

var textAsArray = text.ToArray();
Console.WriteLine(textAsArray);

# Example

Let's now use these methods to not guess where a string is, but to do it programmatically:

var term = "warm";
var position = text.IndexOf(term);
if (position > -1)
{   
    text = text.Insert(position + term.Length, " sunny");
}
Console.WriteLine(text);

if (text.Contains("foggy"))
    text = text.Replace("foggy", string.Empty);

To make the code cleaner, we can assign the value to a variable:

term = "foggy";
if (text.Contains(term))
    text = text.Replace(term, string.Empty);

# Bye

You can have fun with these methods 😅

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