反序列化数据时，UInt64的值太大或太小

Question

I am posting json string to my method and getting error while deserializing to my class.

Error :

Error converting value -1 to type 'System.Nullable`1[System.UInt64]'. Path 'MyMappings 1 .MySqlColumns[7].size'. Inner Exception : {"Value was either too large or too small for a UInt64."}

Below is my class in which I want to output after deserializing json value :

public class MyMappings
   {
       public string Name { get; set; }
       public List<MysqlColumns> MySqlColumns { get; set; }
   }

public class MySqlColumns
    {
        public string Column { get; set; }
        public string Datatype { get; set; }
        public string IsNullable { get; set; }
        public UInt64? Size { get; set; }
        public UInt64? NumericPrecision { get; set; }
        public UInt64? NumericScale { get; set; }
    }

string myJson =  "MyMappings": [
    {
      "Name": "dbo.Table1",
      "MySqlColumns": [
        {
          "Name": "Address",
          "datatype": "nvarchar",
          "isNullable": "YES",
          "size": -1,
          "numericPrecision": null,
          "numericScale": null
        }]

var deserializeData = JsonConvert.DeserializeObject<MyMappings>(myJson);

Now when user set nvarchar(max) for any columns then I set size as -1 which is setinel value to represent max size. Now reason for setting size as -1 is because while reading column whose size is nvarchar(max) I get setinel value as -1 as per Marc Gravell's comment

I have seen this answer but my question is how do I use it while deserialization. I am using NewtonSoft json .

Update

Reason for specifying size as uint:

Answer 1

The U in types names stands for unsigned that is those values is always positive. So the value -1 is too small to be stored in such a variable. Either change your type to signed Int64 . Or use null as marker for max and interpret it as accordingly while creating your column.

---

As for your update the only thing that you can do is to use null and make your logic interpret it as -1 when needed. As it is sad you can't have your cake and eat it at the same time.

Answer 2

I would add new property (bool) to MySqlColumns class. Lets name it MaxLength. This will be used as a max value marker. You will look at this property if your datatype is nvarchar, varchar or any other type, where you can define length.