How to insert a C# List to database using Dapper.NET

Question

Using dapper, how can I insert a C# List to database. Previously without dapper I used the below code to insert the List values to database.

try
{                
    connection.Open();

    for (int i = 0; i < processList.Count; i++)
    {
        string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@Id, @st_Time, @ed_Time, @td_Time)";
        command = new SqlCommand(processQuery, connection);
        command.Parameters.Add("Id", SqlDbType.Int).Value = processList[i].ID;
        command.Parameters.Add("st_Time", SqlDbType.DateTime).Value = processList[i].ST_TIME;
        command.Parameters.Add("ed_Time", SqlDbType.DateTime).Value = processList[i].ED_TIME;
        command.Parameters.Add("td_Time", SqlDbType.DateTime2).Value = processList[i].TD_TIME;
        dataReader.Close();
        dataReader = command.ExecuteReader();
    }

    connection.Close();
}
catch (SqlException ex)
{
    //--Handle Exception
}

I'm familiar with fetching the data using dapper but this is my first try using insert query.

I tried the below code, using Exceute linked to query but stuck up with looping; I think using dapper tool, there is no need for looping statement.

connection.Execute(processQuery ... );

EDIT:

class ProcessLog
    {
        public int ID { get; set; }
        public DateTime ST_TIME { get; set; }
        public DateTime ED_TIME { get; set; }
        public DateTime TD_TIME { get; set; }
        public string frequency { get; set; }
    }

Please advice on this. FYI: I'm using SQL Server 2008.

Benjamin Hodgson · Accepted Answer · 2017-07-26 10:23:59Z

199

You'd have to do it a little differently. In Dapper, it matches on convention AKA property or field names being identical to SQL parameters. So, assuming you had a MyObject:

public class MyObject
{
    public int A { get; set; }

    public string B { get; set; }
}

And assuming processList = List<MyObject>, You'd want to do this

foreach (var item in processList)
{
    string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
    connection.Execute(processQuery, item);
}

Note that the MyObject property names A and B match the SQL parameter names @A and @B.

If you don't want to rename objects, you can use anonymous types to do the mappings instead of concrete types:

foreach (var item in processList)
{
    string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
    connection.Execute(processQuery, new { A = item.A, B = item.B });
}

EDIT:

Per Marc Gravell's comment, you can also have Dapper do the loop for you:

string processQuery = "INSERT INTO PROCESS_LOGS VALUES (@A, @B)";        
connection.Execute(processQuery, processList);

edited Jul 26, 2017 at 10:23

Benjamin Hodgson

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answered Jun 17, 2013 at 15:08

Haney

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27 Comments

Marc Gravell Over a year ago

Actually, little known fact: dapper will iterate for you; the middle one can be: connection.Execute("INSERT INTO PROCESS_LOGS VALUES (@A, @B)", processList);

Steve Over a year ago

My god, Marc you never stop to amaze me. Now I have to go and re-check all the code I've written in the past 10 days. (Since I decided to try this little gem)

Chris Over a year ago

Is there any way to simulate (@a1, @b1),(@a2, @b2) with Dapper? I'm trying to use SQL Server MERGE tble USING VALUES (('a1', 'b1'),('a2','b2')) AS foo(a,b) ON tble.a=foo.a WHEN MATCHED.... If not I'd rather iterate and run many statements than use a temp table, but Dapper creating my bracketed list would be very nice. Am doubtful as I think it is vendor specific. Although MySQL uses comma-delimited brackets to do multiple row inserts so perhaps it isn't? (INS INTO tbl (a,b) VALUES (a1,b1),(a2,b2)).

Marc Gravell Over a year ago

@Mackan dapper won't, but LINQ: use listOfChildren.Select(childId => new { A = parentId, B = childId}) as the arg

niico Over a year ago

Anyone know if this does n round trips / execute to SQL server or does it neatly create 1 insert statement with multiple inserts? Surely the former will be very inefficient, specially if it's a long list?!

|

Community · Accepted Answer · 2017-05-23 11:54:56Z

28

I believe the bulk insert is better than iterate the list and insert one by one.

SqlTransaction trans = connection.BeginTransaction();

connection.Execute(@"
insert PROCESS_LOGS(Id, st_Time, ed_Time, td_Time)
values(@Id, @st_Time, @ed_Time, @td_Time)", processList, transaction: trans);

trans.Commit();

Reference: https://stackoverflow.com/a/12609410/1136277

edited May 23, 2017 at 11:54

CommunityBot

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answered Apr 12, 2017 at 18:02

Thalles Noce

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1 Comment

Bob Horn Over a year ago

I don't believe that's a bulk insert. Individual inserts are done. See the comments in the link you provided.

Yaroslav Voznyy · Accepted Answer · 2020-05-06 12:33:37Z

2

Use Dapper.Contrib https://dapper-tutorial.net/insert#example---insert-single ! You can effortlessly insert list of objects in db.

answered May 6, 2020 at 12:33

Yaroslav Voznyy

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