需要安装 nuget 包 DapperExtensions

代码：

public static void InsertBatchTest<T>(IDbConnection conn, IEnumerable<T> entityList, IDbTransaction transaction = null) where T : class
{
    var tbName = string.Format("dbo.{0}", typeof(T).Name);
    var trans = (SqlTransaction)transaction;
    using (var bulkCopy = new SqlBulkCopy(conn as SqlConnection, SqlBulkCopyOptions.TableLock, trans))
    {
        bulkCopy.BatchSize = 10000;
        bulkCopy.BulkCopyTimeout = 60;
        bulkCopy.DestinationTableName = tbName;
        var table = new DataTable();
        DapperExtensions.Sql.ISqlGenerator sqlGenerator = new SqlGeneratorImpl(new DapperExtensionsConfiguration());
        var classMap = sqlGenerator.Configuration.GetMap<T>();
        var props = classMap.Properties.Where(x => x.Ignored == false).ToArray();
        foreach (var propertyInfo in props)
        {
            bulkCopy.ColumnMappings.Add(propertyInfo.Name, propertyInfo.Name);
            table.Columns.Add(propertyInfo.Name, Nullable.GetUnderlyingType(propertyInfo.PropertyInfo.PropertyType) ?? propertyInfo.PropertyInfo.PropertyType);
        }
        var values = new object[props.Count()];
        foreach (var itemm in entityList)
        {
            for (var i = 0; i < values.Length; i++)
            {
                values[i] = props[i].PropertyInfo.GetValue(itemm, null);
            }
            table.Rows.Add(values);
        }
                
        bulkCopy.WriteToServer(table);
    }
}

2023/09/26 更新

        public static Task InsertBatchTest<T>(this IDbConnection conn, IEnumerable<T> entityList, IDbTransaction transaction = null) where T : class
        {
            if (!entityList.Any()) return Task.CompletedTask;

            var tbName = string.Format("dbo.{0}", typeof(T).Name);
            var trans = (SqlTransaction)transaction;
            using (var bulkCopy = new SqlBulkCopy(conn as SqlConnection, SqlBulkCopyOptions.TableLock, trans))
            {
                bulkCopy.BatchSize = 10000;
                bulkCopy.BulkCopyTimeout = 60;
                bulkCopy.DestinationTableName = tbName;
                var table = new DataTable();
                DapperExtensions.Sql.ISqlGenerator sqlGenerator = new SqlGeneratorImpl(new DapperExtensionsConfiguration());
                var classMap = sqlGenerator.Configuration.GetMap<T>();
                var memberMaps = classMap.Properties.Where(x => x.Ignored == false).ToArray();
                foreach (var memberMap in memberMaps)
                {
                    bulkCopy.ColumnMappings.Add(memberMap.Name, memberMap.Name);
                    table.Columns.Add(memberMap.Name, Nullable.GetUnderlyingType(memberMap.MemberType) ?? memberMap.MemberType);
                }
                var values = new object[memberMaps.Count()];
                var type = typeof(T);
                foreach (var itemm in entityList)
                {
                    for (var i = 0; i < values.Length; i++)
                    {
                        values[i] = type.GetProperty(memberMaps[i].Name).GetValue(itemm, null);
                    }
                    table.Rows.Add(values);
                }

                return bulkCopy.WriteToServerAsync(table);
            }
        }