How to encode the plus (+) symbol in a URL

The + character has a special meaning in a URL => it means whitespace - . If you want to use the literal + sign, you need to URL encode it to %2b:

body=Hi+there%2bHello+there

Here's an example of how you could properly generate URLs in .NET:

var uriBuilder = new UriBuilder("https://mail.google.com/mail");

var values = HttpUtility.ParseQueryString(string.Empty);
values["view"] = "cm";
values["tf"] = "0";
values["to"] = "[email protected]";
values["su"] = "some subject";
values["body"] = "Hi there+Hello there";

uriBuilder.Query = values.ToString();

Console.WriteLine(uriBuilder.ToString());

The result

https://mail.google.com:443/mail?view=cm&tf=0&to=someemail%40somedomain.com&su=some+subject&body=Hi+there%2bHello+there

If you want a plus + symbol in the body you have to encode it as 2B.

For example: Try this