c# - LINQ to SQL 中的强制转换无效

Question

我在使用 LINQ to SQL 时抛出了一个无效的转换异常。这是我在 C# 中的类(class):

[Table(Name = "tbl_request$")]
public class request
{
    [Column(IsPrimaryKey = true)]
    public float requestID;
    [Column]
    public string moduleCode;
    [Column]
    public float park;
    [Column]
    public string requestedRoom;
    [Column]
    public float week;
    [Column]
    public float day;
    [Column]
    public float period;
    [Column]
    public float status;
    [Column]
    public float semester;
    [Column]
    public float priority;
    [Column]
    public float adhoc;
    [Column]
    public float numStudents;
    [Column]
    public float collectionID;
    [Column]
    public float roomCount;
}

这个对应的数据库表

requestID   float   Unchecked
moduleCode  nvarchar(255)   Checked
park    float   Checked
requestedRoom   nvarchar(255)   Checked
week    float   Checked
day float   Checked
period  float   Checked
status  float   Checked
semester    float   Checked
priority    float   Checked
adhoc   float   Checked
numStudents float   Checked
collectionID    float   Checked
roomCount   float   Checked

我觉得一切都很好。还有其他建议吗？

Specified cast is not valid.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidCastException: Specified cast is not valid.

Source Error: 

Line 12:             var bookingtable = Database.DatabaseContext.GetTable<Database.request>();
Line 13:             var dict = new System.Collections.Generic.Dictionary<int, System.Collections.Generic.List<Database.request>>();
Line 14:             foreach (var request in bookingtable)
Line 15:             {
Line 16:                 if (dict[(int)request.collectionID] == null)

堆栈跟踪深入 LINQ 内部。

Answer 1

原来 C# 想要一个 double? 而不是 float?，即使 DB 类型是 FLOAT。