What is the string length of a GUID? or uniqueidentifier data type - char(36)

It depends on how you format the Guid:

• Guid.NewGuid().ToString() => 36 characters (Hyphenated)
  outputs: 12345678-1234-1234-1234-123456789abc
• Guid.NewGuid().ToString("D") => 36 characters (Hyphenated, same as ToString())
  outputs: 12345678-1234-1234-1234-123456789abc

and

• Guid.NewGuid().ToString("N") => 32 characters (Digits only)
  outputs: 12345678123412341234123456789abc
• Guid.NewGuid().ToString("B") => 38 characters (Braces)
  outputs: {12345678-1234-1234-1234-123456789abc}
• Guid.NewGuid().ToString("P") => 38 characters (Parentheses)
  outputs: (12345678-1234-1234-1234-123456789abc)
• Guid.NewGuid().ToString("X") => 68 characters (Hexadecimal)
  outputs: {0x12345678,0x1234,0x1234,{0x12,0x34,0x12,0x34,0x56,0x78,0x9a,0xbc}}

Store is as Char(36) for best performance