Bulk Update in C#

Solution 1:

What I've done before is perform a bulk insert from the data into a temp table, and then use a command or stored procedure to update the data relating the temp table with the destination table. The temp table is an extra step, but you can have a performance gain with the bulk insert and massive update if the amount of rows is big, compared to updating the data row by row.

Example:

public static void UpdateData<T>(List<T> list,string TableName)
{
    DataTable dt = new DataTable("MyTable");
    dt = ConvertToDataTable(list);

    using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["SchoolSoulDataEntitiesForReport"].ConnectionString))
    {
        using (SqlCommand command = new SqlCommand("", conn))
        {
            try
            {
                conn.Open();

                //Creating temp table on database
                command.CommandText = "CREATE TABLE #TmpTable(...)";
                command.ExecuteNonQuery();

                //Bulk insert into temp table
                using (SqlBulkCopy bulkcopy = new SqlBulkCopy(conn))
                {
                    bulkcopy.BulkCopyTimeout = 660;
                    bulkcopy.DestinationTableName = "#TmpTable";
                    bulkcopy.WriteToServer(dt);
                    bulkcopy.Close();
                }

                // Updating destination table, and dropping temp table
                command.CommandTimeout = 300;
                command.CommandText = "UPDATE T SET ... FROM " + TableName + " T INNER JOIN #TmpTable Temp ON ...; DROP TABLE #TmpTable;";
                command.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                // Handle exception properly
            }
            finally
            {
                conn.Close();
            }
        }
    }
}

Notice that a single connection is used to perform the whole operation, in order to be able to use the temp table in each step, because the scope of the temp table is per connection.

Solution 2:

In my personal experience, the best way to handled this situation is utilizing a Stored Procedure with a Table-Valued Parameter and a User-Defined Table Type. Just set up the type with the columns of the data table, and pass in said-data table as a parameter in the SQL command.

Within the Stored Procedure, you can either join directly on some unique key (if all rows you are updating exist), or - if you might run into a situation where you are having to do both updates and inserts - use the SQL Merge command within the stored procedure to handle both the updates and inserts as applicable.

Microsoft has both syntax reference and an article with examples for the Merge.

For the .NET piece, it's a simple matter of setting the parameter type as SqlDbType.Structured and setting the value of said-parameter to the Data Table that contains the records you want to update.

This method provides the benefit of both clarity and ease of maintenance. While there may be ways that offer performance improvements (such as dropping it into a temporary table then iterating over that table), I think they're outweighed by the simplicity of letting .NET and SQL handle transferring the table and updating the records itself. K.I.S.S.