Why strings are immutable in .NET?

Hi all,

what does type String is immutable mean?

I did an assignment on that:

string s;

s = "car";
s += "bus"....

And then,

StringBuilder sb = new StringBuilder(10);

sb.Append("car")
sb.Append("bus")

But both give the same result.

It is said that StringBuilder is there to create dynamic strings.
But I feel like we can use string to do the same thing with out any issue.

• Can anyone give me a good example to differentiate between string and stringbuilder?
• What is the difference between String and StringBuilder?
• Why Strings are immutable?
• Why we use new key word only to declare StringBuilder and not with string declaration?

Please help me to resolve this.

Thanks and Regards,
Jay.