convert list to json format in c#

In C#, I fill a list List jobs = new List(); with objects that hold job opportunities.

I want convert "jobs" to JSON format like this:

{
"Job Title":{
"Sex":"...",
"City":"...",
"Date":"...",
"ActivityField":"...",
"Salary":"...",
"WorkHours":"...",
"Insurance":"..."
"Address":"..."
},
.
.
.
.
}

How can i do that?

I tried but i got this result:

[
{
"JobTitle":"...",
"Sex":"...",
"City":"...",
"Date":"...",
"ActivityField":"...",
"Salary":"... ",
"WorkHours":"...",
"Insurance":"...",
"Address":"...
},
.
.
.
.
]