How to insert C# variable value in between string properly?

Here are the ways to insert C# variable in between a string:

1. Using string.Format
   

   var str="<span href='/ShowQuote/{0}?NewTab=True' style='margin: 10px; text-decoration:none' class='ShowQuoteClick'>Fetched one quote for {1} with Id-{2}</span>";
   var newStr=string.Format(str, QID,MainCompanyName,Id);?

2. Using C# 6.0 String Interpolation
   

   var QID= "1";
   var MainCompanyName = "Test";
   var Id="11";
   var str = $"<span href='/ShowQuote/{QID}?NewTab=True' style='margin: 10px; text-decoration:none' class='ShowQuoteClick'>Fetched one quote for {MainCompanyName} with Id-{Id}</span>";
   

You can check the detailed article on C# String Interpolation here or about C# Strings

Basically, you can format strings using String.Format as sample is provided in above answer.

            string name = "Vikas";
            string developer = ".NET Developer";
            Console.WriteLine(String.Format("Hi my name is {0}, working as {1}",
                                          name, developer));

Hope it helps.