Insert a list using dapper.NET C#

Question

I'd like to insert a list of objects in an SQL table.

I know this question here but I don't understand.

Here is my class :

public class MyObject 
{
    public int? ID { get; set; }
    public string ObjectType { get; set; }
    public string Content { get; set; }
    public string PreviewContent { get; set; }

    public static void SaveList(List<MyObject> lst)
    {
        using (DBConnection connection = new DBConnection())
        {
            if (connection.Connection.State != ConnectionState.Open)
                connection.Connection.Open();

            connection.Connection.Execute("INSERT INTO [MyObject] VALUE()",lst);                
        }
    }
}

I'd like to know how could I insert my list using Dapper, I don't want to iterate on the list and save them one by one, I would like to insert all of them in one request.

score 22 · Accepted Answer · answered May 16 '17 at 14:02

22

You can insert these just as you would INSERT a single line:

public class MyObject 
{
    public int? ID { get; set; }
    public string ObjectType { get; set; }
    public string Content { get; set; }
    public string PreviewContent { get; set; }

    public static void SaveList(List<MyObject> lst)
    {
        using (DBConnection connection = new DBConnection())
        {
            if (connection.Connection.State != ConnectionState.Open)
                connection.Connection.Open();

            connection.Connection.Execute("INSERT INTO [MyObject] (Id, ObjectType, Content, PreviewContent) VALUES(@Id, @ObjectType, @Content, @PreviewContent)", lst);                
        }
    }
}

Dapper will look for class members named after your SQL parameters (@Id, @ObjectType, @Content, @PreviewContent) and bind them accordingly.

answered May 16 '17 at 14:02

Pierre-Loup Pagniez

3,611
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29

It works, but for 1000 objects, it's still slow, exactly the same when i used iteration over the list and save them one by one :/ – Vincent Ducroquet May 16 '17 at 14:08
2

Try this answer to see if it helps with performance: http://stackoverflow.com/a/12609410/1166719. By the way, hi! Long time no see :) – Pierre-Loup Pagniez May 16 '17 at 14:11
2

This creates a request per item in the list, thereby not solving the question. – Ykok Jan 04 '21 at 14:44

Daniel Tshuva · Answer 2 · 2017-05-16T14:16:35.510

You need pass a table-value parameter.
1. Create table type in your sql database.
2. Create DynamicParameters and add the datatable (new values) to it.
3. Execute.

SQL:

CREATE TYPE [dbo].[tvMyObjects] AS TABLE(
    [ID] INT,
    [ObjectType] [varchar](70), /*Length on your table*/
    [Content] [varchar](70), /*Length on your table*/
    [PreviewContent] [varchar](70) /*Length on your table*/
)

C#:

var dynamicParameters = new DynamicParameters();
dynamicParameters.Add("@MyObjects", lst
    .AsTableValuedParameter("dbo.tvMyObjects", new[] 
    {
        "ID" ,
        "ObjectType",
        "Content", 
        "PreviewContent"
    }));

connection.Connection.Execute(@"
    INSERT INTO [MyObject] (Id, ObjectType, Content, PreviewContent) 
    SELECT Id,
           ObjectType,
           Content,
           PreviewContent
    FROM   @MyObjects", dynamicParameters);

More info: https://www.codeproject.com/Articles/835519/Passing-Table-Valued-Parameters-with-Dapper

lst is List (it's from the question). The AsTableValuedParameter function transform a list to datatable (https://www.codeproject.com/Articles/835519/Passing-Table-Valued-Parameters-with-Dapper) — Daniel Tshuva, Aug 24 '17 at 13:19

Charles Mager · Answer 3 · 2017-05-16T14:04:06.983

0

You would just change your SQL to a valid insert statment that has parameters matching the names of the properties on your class.

INSERT INTO MyObject VALUES(@Id, @ObjectType, @Content, @PreviewContent)

Or if you need to specify the table columns (where these aren't all the columns in the table, for example):

INSERT INTO MyObject (Id, ObjectType, Content, PreviewContent)
VALUES(@Id, @ObjectType, @Content, @PreviewContent)

edited May 16 '17 at 14:04

answered May 16 '17 at 13:59

Charles Mager

25,735
2
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The question was about insert a list in bulk to database. no with loop in c# code. – Daniel Tshuva Aug 24 '17 at 13:24
@DanielTshuva this is the same as the accepted answer? – Charles Mager Aug 24 '17 at 13:27

Ron · Answer 4 · 2017-07-28T14:21:02.687

You can use the Dapper.Contrib extensions to simplify the code. I've found this works well for a few hundred records, but for very large inserts, I switch to SqlBulkCopy. The synchronous version is Insert instead of InsertAsync (as you'd guess). Make sure your entities are named as Dapper expects and have a primary key, Id, or, add annotations for table name and key to your entity.

using using Dapper.Contrib.Extensions; //Git

public async Task SaveChangesAsync(IList<MyEntity> myEntityValues)
{
     var conn = new SqlConnection(myconnectionString);
     if(conn.State != ConnectionState.Open)
         conn.Open();
     await conn.InsertAsync(myEntityValues);
     if (conn.State != ConnectionState.Closed)
     {
        conn.Close();
        conn.Dispose();
      }
}

While this code works, it should ideally instantiate the connection in a `using` statement, or wrap it in a `using` block, to ensure it gets closed and disposed correctly. — Patrick Tucci, May 15 '21 at 15:43

John Jang · Answer 5 · 2021-04-27T03:58:59.543

In case you need new naming or combined sources:

await connection.ExecuteAsyncWithRetry(SqlSave,
     list.Select(x => 
            new
            {
                x.ID,
                SomeNew = NewSource.SomeNew,  // From other source
                NameNew = x.NameOld,  // New naming
                x.ObjectType,
                x.Content,
                x.ContentList = String.Join(",", x.Content)  // Data transform
            }));

Insert a list using dapper.NET C#

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