LINQ to SQL中的无效转换

Question

我使用LINQ to SQL抛出了无效的强制转换异常。这是我在C＃中的课程：

[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;
}

数据库表格对应

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

一切看起来都不错。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

事实证明，即使数据库类型为double?，C＃也需要float?而不是FLOAT。