CompanyList.json

"CompanyList" : [
{
    "Name": "Optiim",
    "Address": "Blablala",
    "PhoneNumber": "0123456789",
},
{
    "Name": "Matriks",
    "Address": "Blablala",
    "PhoneNumber": "0123456789",
}]

Test.cs

// Ornek Company sinifi boyle olsun;
public class Company
{
	public string Name { get; set; }
	public string Address { get; set; }
	public string PhoneNumber { get; set; }
}

// ...

// GetCompanyListJson() metodu json string'ini veriyor olsun.
string jsonStr = GetCompanyListJson();

// Json'dan listeye boyle donusturulur;
List<Company> companyList = Newtonsoft.Json.JsonConvert.DeserializeObject<List<Company>>(jsonStr);

// Object'den Json uretmek şstersen de;
string jsonStr2 = Newtonsoft.Json.JsonConvert.SerializeObject(companyList);