C#中$的用法

C#中$的用法是c#6.0后新增的特性，用于代替string.Format("")，例如：

string strWhere="";

strWhere += string.Format(" and w.Id={0}", searchKeys["Id"].ToString());
strWhere += $" and w.Id={searchKeys["Id"].ToString()}";
strWhere += $" and w.Id='{searchKeys["Id"].ToString()}'";
strWhere += $" and w.Id=\"{searchKeys["Id"].ToString()}\"";