# String method

## ToUpper

set strings uppercase

```C#
String fullName = "mrsh"; 
fullName = fullName.ToUpper();

```

## Tolower

set strings lowercase

```C#
String fullName = "mrsh"; 
fullName = fullName.ToLower();
```

## Replace

```C#
String phoneNumber = "123-456-789"; 
phoneNumber.Replace("-", "/");
```

## Insert

```C#
String fullName = "mrsh online"; 
userName = fullName.Insert(0, "@");
```

## Length

```C#
String fullName = "mrsh online"; 
fullName.Length();
```

## Substring

```C#
String fullName = "mrsh online"; 
String firstName = fullName.Substring(0,4); 
String lastName = fullName.Substring(5,6); 
```

## String interpolation

```C#
String firstName = "mrsh";
String lastName = "Online";
int age = 21;

Console.WriteLine($"Hello {firstName} {lastName}.");

// include 10 spaces
Console.WriteLine($"You are {age, 10} years old.");
```