how to handle null exception in C#

im getting null exception . while im directly exceciting this page. i want to handle null exception

C# 

string json = "";
if (Request.QueryString["data"] !="")
{
    json = Request.QueryString["data"];

    var req = JsonConvert.DeserializeObject<Request>(json);//getting error in this line
    string requestid = req.requestId;
    SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["MYSTRING"].ConnectionString);
    SqlCommand cmd = new SqlCommand();
    connection.Open();
}

error

Value cannot be null. Parameter name: value

Jon Skeet
people
quotationmark

Well presumably Request.QueryString["data"] is null. You're currently checking whether it's a reference to an empty string, but not whether it's a null reference. I suspect you want to use string.IsNullOrEmpty to check that:

string json = Request.QueryString["data"];
if (!string.IsNullOrEmpty(json))
{
     var req = JsonConvert.DeserializeObject<Request>(json);
     ...
}

people

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