Nullable的EditorFor <long> 将修剪分数

Question

I have the following model class inside my asp.net mvc web application :-

[Display(Name="RAM (in GB)")]
        public Nullable<long> TOTALMEMORY { get; set; }

which represents total memery in bytes. now i need to convert bytes to GB , by doing the following on my controller class :-

.MemoryInfo.TOTALMEMORY = (server.SystemInfo.MemoryInfo.TOTALMEMORY / (1024 * 1024 * 1024));

Then on the view the will display using the following two syntax as follow:-

@Html.EditorFor(model =>model.SystemInfo.MemoryInfo.VIRTUALMEMORY) 

OR

@(Model.SystemInfo.MemoryInfo == null ? "" : Model.SystemInfo.MemoryInfo.TOTALMEMORY.ToString())

so in both way if the value in the DB is 8583778304 it will be displayed as 7 instead of 7.99 on the razor view ? can anyone adivce what is the problem ?

EDIT currently the

@Html.EditorFor(model =>model.SystemInfo.MemoryInfo.TotalMemoryGB)

will display 7.99426651000977 instead of 7.99

while @(Model.SystemInfo.MemoryInfo == null ? "" : Model.SystemInfo.MemoryInfo.TotalMemoryGB.ToString()) will display 6.51925802230835E-09 . so can you advice ?

Answer 1

TOTALMEMORY is a long value, which means it is an 64-bit integer. It simply cannot house a decimal number like 7.99. And since you use integer division, it will always just trim the result, ie ignore everything after the decimal point.

If the decimals are important to you, change it to a nullable double

public double? TOTALMEMORY { get; set; }

or even better, leave the field as is, to keep the EF mappings, and add a calculated property that connects to it:

public long? TOTALMEMORY { get; set; }

[Display(Name="RAM (in GB)")]
public double? TotalMemoryGB 
{
   get 
   {
       // The 1024.0 serves to force double division, instead of integer
       return TOTALMEMORY / 1024.0 / 1024.0 / 1024.0;
   }
   set 
   {
       TOTALMEMORY = (long) (value * 1024 * 1024 * 1024);
   } 
}

Now, in your UI you can use TotalMemoryGB exlusively, and work in gigabytes, while preserving the bytes in the database.