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+# 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); 
+```