用“Dapper不支持的类”插入带有Dapper错误的IEnumerable<T>集合。

Question

是的，有这里的问题和这里关于如何使用dapper插入记录.然而，这些答案虽然内容丰富，但似乎并没有给我指明正确的方向。情况如下:将数据从SqlServer移动到MySql。将记录读入IEnumerable<WTUser>是很容易的，但我只是没有从插入中得到一些东西。首先，“移动记录代码”：

//  moving data
Dim session As New Session(DataProvider.MSSql, "server", _
                           "database")

Dim resources As List(Of WTUser) = session.QueryReader(Of WTUser)("select * from tbl_resource")


session = New Session(DataProvider.MySql, "server", "database", _
                      "user", "p@$$w0rd")

//    *edit* - corrected parameter notation with '@'
Dim strInsert = "INSERT INTO tbl_resource (ResourceName, ResourceRate, ResourceTypeID, ActiveYN) " & _
                "VALUES (@ResourceName, @ResourceRate, @ResourceType, @ActiveYN)"

Dim recordCount = session.WriteData(Of WTUser)(strInsert, resources)

//  session Methods
    Public Function QueryReader(Of TEntity As {Class, New})(ByVal Command As String) _
                                                            As IEnumerable(Of TEntity)
        Dim list As IEnumerable(Of TEntity)

        Dim cnn As IDbConnection = dataAgent.NewConnection
        list = cnn.Query(Of TEntity)(Command, Nothing, Nothing, True, 0, CommandType.Text).ToList()

        Return list
    End Function

    Public Function WriteData(Of TEntity As {Class, New})(ByVal Command As String, ByVal Entities As IEnumerable(Of TEntity)) _
                                                          As Integer
        Dim cnn As IDbConnection = dataAgent.NewConnection

        //    *edit* if I do this I get the correct properties, but no data inserted
        //Return cnn.Execute(Command, New TEntity(), Nothing, 15, CommandType.Text)

        //    original Return statement
        Return cnn.Execute(Command, Entities, Nothing, 15, CommandType.Text)
    End Function

cnn.Query和cnn.Execute调用dapper扩展方法。现在，WTUser类(注意:列名从SqlServer中的“WindowsName”更改为MySql中的“ResourceName”，因此两个属性指向相同的字段)：

Public Class WTUser
    //    edited for brevity - assume the following all have public get/set methods
    Public ActiveYN As String
    Public ResourceID As Integer
    Public ResourceRate As Integer
    Public ResourceType As Integer
    Public WindowsName As String
    Public ResourceName As String

End Class

我收到了Dapper的一个异常：“Dapper不支持WTUser。”这种方法在DataMapper (Dapper)中：

    private static Action<IDbCommand, object> CreateParamInfoGenerator(Type OwnerType)
    {
        string dmName = string.Format("ParamInfo{0}", Guid.NewGuid());
        Type[] objTypes = new[] { typeof(IDbCommand), typeof(object) };

        var dm = new DynamicMethod(dmName, null, objTypes, OwnerType, true); // << - here
        //    emit stuff

        //    dm is instanced, now ...
        foreach (var prop in OwnerType.GetProperties().OrderBy(p => p.Name))

此时OwnerType =

System.Collections.Generic.List`1[CRMBackEnd.WTUser，CRMBE，Version=1.0.0.0，Culture=neutral，PublicKeyToken=null]，Version=2.0.0.0，Culture=neutral，PublicKeyToken=b77a5c561934e089

看来OwnerType应该是CRMBackEnd.WTUser ..。不是List<CRMBackEnd.WTUser> .？因为正在发生的是正在迭代集合属性:计数、容量等。，我缺少什么？

更新

如果我将session.WriteData修改为：

Public Function WriteData(Of TEntity As {Class, New})(ByVal Command As String, _
                                                      ByVal Entities As IEnumerable(Of TEntity)) _
                                                      As Integer
    Dim cnn As IDbConnection = dataAgent.NewConnection
    Dim records As Integer

    For Each entity As TEntity In Entities
        records += cnn.Execute(Command, entity, Nothing, 15, CommandType.Text)
    Next

    Return records
End Function

记录插入得很好..。但我认为没有必要举这样的例子：

connection.Execute(@"insert MyTable(colA, colB) values (@a, @b)",
    new[] { new { a=1, b=1 }, new { a=2, b=2 }, new { a=3, b=3 } }
  ).IsEqualTo(3); // 3 rows inserted: "1,1", "2,2" and "3,3"  

..。来自脱衣舞网

Answer 1

我刚加入了一个测试：

class Student
{
    public string Name {get; set;}
    public int Age { get; set; }
}

public void TestExecuteMultipleCommandStrongType()
{
    connection.Execute("create table #t(Name nvarchar(max), Age int)");
    int tally = connection.Execute(@"insert #t (Name,Age) values(@Name, @Age)", new List<Student> 
    {
        new Student{Age = 1, Name = "sam"},
        new Student{Age = 2, Name = "bob"}
    });
    int sum = connection.Query<int>("select sum(Age) from #t drop table #t").First();
    tally.IsEqualTo(2);
    sum.IsEqualTo(3);
}

就像广告上说的那样。我对multi的工作方式做了一些修改(所以它更快一些，并且支持object[])。

我猜您有问题，因为您在WTUser上的所有字段中都缺少一个getter属性。所有params都必须有读取器属性，我们不支持从字段中提取它，它需要一个复杂的解析步骤才能保持效率。

另一个引起问题的点是通过不支持映射的param传递dapper。

例如，以下类不支持param：

class Test
{
   public int Id { get; set; }
   public User User {get; set;}
}

cnn.Query("select * from Tests where Id = @Id", new Test{Id = 1}); // used to go boom 

问题是，dapper没有对进行解析，而是假定所有道具都可以作为params设置，但无法解决User的SQL类型。

最新的rev解决了这一问题。