SqlServerCompact 4.0 无法在 WPF App 中使用 entity framework 的所有功能

Question

我在我的 WPF 应用程序中使用 EntityFramework.SQLServerCompact nuget 包。

它确实部分起作用，例如：

确实如此运行 ToList()。

它没有运行 Where() 查询，它显示了这个异常：

SqlCeException: The specified argument value for the function is not valid. [ Argument # = 3,Name of function(if known) = case ]

当我运行以下查询时：

_db.Users.Where(x => x.Email == email_input.Text.ToString() && x.Password == password_input.Password.ToString())

它运行的查询是：

SELECT 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[Email] AS [Email], 
    [Extent1].[Phone] AS [Phone], 
    [Extent1].[Password] AS [Password], 
    [Extent1].[CreatedAt] AS [CreatedAt]
    FROM [Users] AS [Extent1]
    WHERE ([Extent1].[Email] = (CASE WHEN (cast(@p__linq__0 as ntext) IS NULL) THEN N'' ELSE @p__linq__0 END)) AND ([Extent1].[Password] = (CASE WHEN (cast(@p__linq__1 as ntext) IS NULL) THEN N'' ELSE @p__linq__1 END))

Answer 1

不要在谓词中调用 ToString()。在构造查询之前尝试分配字符串：

string email = email_input.Text.ToString(); //isn't Text already a string by the way?
string pwd = password_input.Password.ToString();

var users = _db.Users.Where(x => x.Email == email && x.Password == pwd).ToArray();

请注意，SQL 服务器精简版已被弃用。

SqlServerCompact 4.0 无法在 WPF App 中使用 entity framework 的所有功能

SqlServerCompact 4.0 cannot use all features of entity framework in WPF App

c#

sql-server

wpf

entity-framework-6