插入一个 IEnumerable<T>带有 Dapper 错误的

Inserting an IEnumerablelt;Tgt; collection with Dapper errors out with quot;class is not supported by Dapper.quot;(插入一个 IEnumerablelt;Tgt;带有 Dapper 错误的集合，带有“Dapper 不支持类.)

问题描述

是的，这里有问题和这里了解如何使用 dapper-dot-net 插入记录.然而，这些答案虽然内容丰富，但似乎并没有为我指明正确的方向.情况如下:将数据从 SqlServer 移动到 MySql.将记录读入 IEnumerable<WTUser> 很容易，但我只是在插入时没有得到任何东西.一、'移动记录代码':

Yep, there are questions here and here about how to insert records with dapper-dot-net. However, the answers, while informative, didn't seem to point me in the right direction. Here is the situation: moving data from SqlServer to MySql. Reading the records into an IEnumerable<WTUser> is easy, but I am just not getting something on the insert. First, the 'moving records code':

//  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"，因此两个属性指向同一个字段):

cnn.Query and cnn.Execute call the dapper extension methods. Now, the WTUser class (note: the column name changed from 'WindowsName' in SqlServer to 'ResourceName' in MySql, thus the two properties pointing to the same field):

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

我收到来自 dapper 的异常:Dapper 不支持 WTUser."DataMapper(dapper)中的这个方法:

I am receiving an exception from dapper: "WTUser is not supported by Dapper." This method in DataMapper (dapper):

    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 =

At this point OwnerType =

System.Collections.Generic.List`1[[CRMBackEnd.WTUser,CRMBE，版本=1.0.0.0，文化=中性，PublicKeyToken=null]], mscorlib,版本=2.0.0.0，文化=中性，PublicKeyToken=b77a5c561934e089

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

似乎 OwnerType 应该是 CRMBackEnd.WTUser ...而不是 List ... ???因为正在发生的事情是正在迭代集合属性:计数、容量等.我错过了什么?

It seems like OwnerType should be CRMBackEnd.WTUser ... not List<CRMBackEnd.WTUser> ... ??? because what is happening is that the collection properties are being iterated: Count, Capacity, etc. What am I missing?

更新

如果我将 session.WriteData 修改为:

If I modified session.WriteData as:

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

记录被很好地插入......但我认为这不是必要的，例如:

records are inserted nicely ... but I didn't think this would be necessary given examples like:

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 dapper-dot-net

推荐答案

我刚刚为此添加了一个测试:

I just added a test for this:

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);
}

它像宣传的那样工作.我对 multi-exec 的工作方式进行了一些修改(所以它更快一点并且支持 object[]).

It works as advertised. I made a few amendments to the way multi-exec works (so its a tad faster and supports object[]).

我的猜测是您遇到了问题，因为您在 WTUser 上的所有字段上都缺少 getter 属性.所有参数都必须具有读取器属性，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.

My guess is you were having issues cause you were missing a getter property on all you fields on WTUser. All params must have reader properties, we do not support pulling this from fields, it would require a complex parsing step to stay efficient.

导致问题的另一点是向 dapper 传递一个带有不受支持的映射的参数.

An additional point that caused an issue is passing dapper a param with unsupported mapping.

例如，不支持以下类作为参数:

For example, the following class is not supported as a 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 没有解析 SQL，它假定所有的 props 都可以设置为参数，但无法解析 User 的 SQL 类型.

The issue is that dapper did not parse the SQL, it assumed all the props are settable as params but was unable to resolve the SQL type for User.

最新版本解决了这个问题

Latest rev resolves this

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