Bulk Insert of Generic List C# into SQL Server

Question

How can I bulk insert a generic list in c# into SQL Server, rather than looping through the list and inserting individual items one at a time?

I currently have this;

private void AddSnapshotData()
{
  var password =       Cryptography.DecryptString("vhx7Hv7hYD2bF9N4XhN5pkQm8MRfxi+kogALYqwqSuo=");
  var figDb = "ZEUS";
  var connString =
    String.Format(
      "Data Source=1xx.x.xx.xxx;Initial Catalog={0};;User ID=appuser;Password={1};MultipleActiveResultSets=True",
      figDb, password);
  var myConnection = new SqlConnection(connString);
  myConnection.Open();

  foreach (var holding in _dHoldList)
  {
    lbStatus.Text = "Adding information to SQL for client: " + holding.ClientNo;
    _reports.AddZeusData("tblAllBrooksHoldingsSnapshot", "CliNo, SEDOL, ISIN, QtyHeld, DateOfSnapshot",
                         "'" + holding.ClientNo + "','" + holding.Sedol + "','" + holding.ISIN + "','" +
                         holding.QuantityHeld + "','" + DateTime.Today.ToString("yyyyMMdd") + "'", false, myConnection);
  }
  myConnection.Close();
  lbStatus.Visible = false;
}

Where dHoldList is a list of DHOLDS;

public class DHOLDS : ExcelReport
 {
public String ClientNo { get; set; }
public String Sedol { get; set; }
public Double QuantityHeld { get; set; }
public Double ValueOfStock { get; set; }
public String Depot { get; set; }
public String ValC4 { get; set; }
public String StockR1 { get; set; }
public String StockR2 { get; set; }
public Double BookCost { get; set; }
public String ISIN { get; set; }
}

Answer 1

You may map your list to a datatable and then use SqlBulkCopy to insert all the rows at once.

Answer 2

4 years later this is my contribution. I had the same problem, I wanted to to bulk insert but passing over some fields that weren't going to be in the database, specifically EF navigation properties, so I wrote this generic class:

/// <summary>
/// This class is intended to perform a bulk insert of a list of elements into a table in a Database. 
/// This class also allows you to use the same domain classes that you were already using because you
/// can include not mapped properties into the field excludedPropertyNames.
/// </summary>
/// <typeparam name="T">The class that is going to be mapped.</typeparam>
public class BulkInsert<T> where T : class
{
    #region Fields

    private readonly LoggingService _logger = new LoggingService(typeof(BulkInsert<T>));
    private string _connectionString;
    private string _tableName;
    private IEnumerable<string> _excludedPropertyNames;
    private int _batchSize;
    private IEnumerable<T> _data;
    private DataTable _dataTable;

    #endregion

    #region Constructor

    /// <summary>
    /// Initializes a new instance of the <see cref="BulkInsert{T}"/> class.
    /// </summary>
    /// <param name="connectionString">The connection string.</param>
    /// <param name="tableName">Name of the table.</param>
    /// <param name="data">The data.</param>
    /// <param name="excludedPropertyNames">The excluded property names.</param>
    /// <param name="batchSize">Size of the batch.</param>
    public BulkInsert(
        string connectionString,
        string tableName,
        IEnumerable<T> data,
        IEnumerable<string> excludedPropertyNames,
        int batchSize = 1000)
    {
        if (string.IsNullOrEmpty(connectionString)) throw new ArgumentNullException(nameof(connectionString));
        if (string.IsNullOrEmpty(tableName)) throw new ArgumentNullException(nameof(tableName));
        if (data == null) throw new ArgumentNullException(nameof(data));
        if (batchSize <= 0) throw new ArgumentOutOfRangeException(nameof(batchSize));

        _connectionString = connectionString;
        _tableName = tableName;
        _batchSize = batchSize;
        _data = data;
        _excludedPropertyNames = excludedPropertyNames == null ? new List<string>() : excludedPropertyNames;
        _dataTable = CreateCustomDataTable();
    }

    #endregion

    #region Public Methods

    /// <summary>
    /// Inserts the data with a bulk copy inside a transaction. 
    /// </summary>
    public void Insert()
    {
        using (var connection = new SqlConnection(_connectionString))
        {
            connection.Open();
            SqlTransaction transaction = connection.BeginTransaction();

            using (var bulkCopy = new SqlBulkCopy(connection, SqlBulkCopyOptions.Default | SqlBulkCopyOptions.KeepIdentity, transaction))
            {
                bulkCopy.BatchSize = _batchSize;
                bulkCopy.DestinationTableName = _tableName;

                // Let's fix tons of mapping issues by
                // Setting the column mapping in SqlBulkCopy instance:
                foreach (DataColumn dataColumn in _dataTable.Columns)
                {
                    bulkCopy.ColumnMappings.Add(dataColumn.ColumnName, dataColumn.ColumnName);
                }

                try
                {
                    bulkCopy.WriteToServer(_dataTable);
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex.Message);
                    transaction.Rollback();
                    connection.Close();
                }
            }

            transaction.Commit();
        }
    }

    #endregion

    #region Private Helper Methods

    /// <summary>
    /// Creates the custom data table.
    /// </summary>
    private DataTable CreateCustomDataTable()
    {
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));
        var table = new DataTable();
        foreach (PropertyDescriptor prop in properties)
        {
            // Just include the not excluded columns
            if (_excludedPropertyNames.All(epn => epn != prop.Name))
            {                  
                if (prop.PropertyType.Name == "DbGeography")
                {
                    var type = typeof(SqlGeography);
                    table.Columns.Add(prop.Name, type);
                }
                else
                {
                    table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
                }
            }
        }
        foreach (T item in _data)
        {
            DataRow row = table.NewRow();
            foreach (PropertyDescriptor prop in properties)
            {
                // Just include the values in not excluded properties 
                if (_excludedPropertyNames.All(epn => epn != prop.Name))
                {
                    if (prop.PropertyType.Name == "DbGeography")
                    {                           
                        row[prop.Name] = SqlGeography.Parse(((DbGeography)prop.GetValue(item)).AsText()).MakeValid();
                    }
                    else
                    {
                        row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
                    }
                }
            }
            table.Rows.Add(row);
        }
        return table;
    }

    #endregion

}

It's usage would be like:

//1st.- You would have a colection of entities:
var myEntities = new List<MyEntity>();
// [...] With thousands or millions of items

// 2nd.- You would create the BulkInsert:
myEntityTypeBulk = new BulkInsert<MyEntity>(_connectionString, "MyEntitiesTableName", myEntities, new[] { "ObjectState", "SkippedEntityProperty1", "SkippedEntityProperty2" });

// 3rd.- You would execute it:
myEntityTypeBulk.Insert();

The performance gained and the reusability of this class were worth this message. I hope it helps:

Juan