問題描述

是的，這里有問題和這里了解如何使用 dapper-dot-net 插入記錄.然而，這些答案雖然內容豐富，但似乎并沒有為我指明正確的方向.情況如下:將數據從 SqlServer 移動到 MySql.將記錄讀入 IEnumerable<WTUser> 很容易，但我只是在插入時沒有得到任何東西.一、'移動記錄代碼':

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 調用 dapper 擴展方法.現在，WTUser 類(注意:列名從 SqlServer 中的WindowsName"更改為 MySql 中的ResourceName"，因此兩個屬性指向同一個字段):

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

我收到來自 dapper 的異常:Dapper 不支持 WTUser."DataMapper(dapper)中的這個方法:

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))

此時 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 應該是 CRMBackEnd.WTUser ...而不是 List ... ???因為正在發生的事情是正在迭代集合屬性:計數、容量等.我錯過了什么?

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

如果我將 session.WriteData 修改為:

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

記錄被很好地插入......但我認為這不是必要的，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"  

...來自 dapper-dot-net

推薦答案

我剛剛為此添加了一個測試:

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);
}

它像宣傳的那樣工作.我對 multi-exec 的工作方式進行了一些修改(所以它更快一點并且支持 object[]).

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

我的猜測是您遇到了問題，因為您在 WTUser 上的所有字段上都缺少 getter 屬性.所有參數都必須具有讀取器屬性，我們不支持從字段中提取它，它需要一個復雜的解析步驟才能保持效率.

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.

導致問題的另一點是向 dapper 傳遞一個帶有不受支持的映射的參數.

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

例如，不支持以下類作為參數:

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 

問題是 dapper 沒有解析 SQL，它假定所有的 props 都可以設置為參數，但無法解析 User 的 SQL 類型.

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.

最新版本解決了這個問題

Latest rev resolves this

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