如何在C#中处理null异常

Question

我得到null异常.虽然我直接超过这个页面.我想处理null异常

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();
}

错误

值不能为空.参数名称:value

Answer 1

很可能Request.QueryString["data"]是空的.您当前正在检查它是否是对空字符串的引用,而不是它是否为空引用.我怀疑你想string.IsNullOrEmpty用来检查:

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