無論是linq to sql 還是entity frameworks，在進行列表操作時都會有一個毛病，那就是它的操作只能一個實體一個實體的發到服務器，這樣，如果列表的數量很大，如列表爲１０萬條數據，那麼，這種操作將是非常性能的，可能你的ＤＢ就掛了。
解決方案：拼接Ｔ—ＳＱＬ串，並使它具有通用性
好處：與服務器建立一次連接，給服務器發一條ＳＱＬ命令，即可實現
代碼如下：
1 /// <summary> 2 /// 構建Insert語句串 3 /// 主鍵爲自增時，如果主鍵值爲0，我們將主鍵插入到SQL串中 4 /// </summary> 5 /// <typeparam name="TEntity"></typeparam> 6 /// <param name="entity"></param> 7 /// <returns></returns> 8 private Tuple<string, object[]> CreateInsertSQL<TEntity>(TEntity entity) where TEntity : class 9 { 10 if (entity == null) 11 throw new ArgumentException("The database entity can not be null."); 12 13 Type entityType = entity.GetType(); 14 var table = entityType.GetProperties().Where(i => i.PropertyType != typeof(EntityKey) 15 && i.PropertyType != typeof(EntityState) 16 && i.GetValue(entity, null) != null 17 && (i.PropertyType.IsValueType || i.PropertyType == typeof(string))) 18 .ToArray();//過濾主鍵，航行屬性，狀態屬性等 19 List<string> pkList = GetPrimaryKey<TEntity>().Select(i => i.Name).ToList(); 20 21 List<object> arguments = new List<object>(); 22 StringBuilder fieldbuilder = new StringBuilder(); 23 StringBuilder valuebuilder = new StringBuilder(); 24 25 fieldbuilder.Append(" INSERT INTO " + string.Format("[{0}]", entityType.Name) + " ("); 26 27 foreach (var member in table) 28 { 29 if (pkList.Contains(member.Name) && Convert.ToString(member.GetValue(entity, null)) == "0") 30 continue; 31 object value = member.GetValue(entity, null); 32 if (value != null) 33 { 34 if (arguments.Count != 0) 35 { 36 fieldbuilder.Append(", "); 37 valuebuilder.Append(", "); 38 } 39 40 fieldbuilder.Append(member.Name); 41 if (member.PropertyType == typeof(string) || member.PropertyType == typeof(DateTime)) 42 valuebuilder.Append("'{" + arguments.Count + "}'"); 43 else 44 valuebuilder.Append("{" + arguments.Count + "}"); 45 if (value.GetType() == typeof(string)) 46 value = value.ToString().Replace("'", "char(39)"); 47 arguments.Add(value); 48 49 } 50 } 51 52 53 fieldbuilder.Append(") Values ("); 54 55 fieldbuilder.Append(valuebuilder.ToString()); 56 fieldbuilder.Append(");"); 57 return new Tuple<string, object[]>(fieldbuilder.ToString(), arguments.ToArray()); 58 }
之後我將陸續把更新操作與刪除操作及對增刪改操作進行封裝，
對於EF架構中的批量更新操作，需要我們爲實體的導航屬性進行手動的標示，因爲EF生成的實體中沒有一個特殊的說明，所以，我們必須要告訴系統，哪個屬性是導航屬性，而導航屬性是我們不去進行update的。
1 /// <summary> 2 /// 屬性的導航屬性 3 /// </summary> 4 public class NavigationAttribute : Attribute 5 { 6 7 }
而對於要進行批量更新的實體，我們需要爲導航屬性添加這個特性
1 public class User 2 { 3 public int UserID { get; set; } 4 [Navigation] 5 public User_Extension User_Extension { get; set; } 6 }
而對於我們構建批量Update語句，請看代碼，它需要對導航屬性進行過濾
1 /// <summary> 2 /// 構建Update語句串 3 /// </summary> 4 /// <typeparam name="TEntity"></typeparam> 5 /// <param name="entity"></param> 6 /// <returns></returns> 7 private Tuple<string, object[]> CreateUpdateSQL<TEntity>(TEntity entity) where TEntity : class 8 { 9 if (entity == null) 10 throw new ArgumentException("The database entity can not be null."); 11 List<string> pkList = GetPrimaryKey<TEntity>().Select(i => i.Name).ToList(); 12 13 Type entityType = entity.GetType(); 14 var table = entityType.GetProperties().Where(i => 15 !pkList.Contains(i.Name) 16 && i.GetValue(entity, null) != null 17 && i.PropertyType != typeof(EntityState) 18 && !(i.GetCustomAttributes(false).Length > 0 19 && i.GetCustomAttributes(false).Where(j => j.GetType() == typeof(NavigationAttribute)) != null) 20 && (i.PropertyType.IsValueType || i.PropertyType == typeof(string)) //過濾導航屬性 21 ).ToArray(); 22 23 //過濾主鍵，航行屬性，狀態屬性等 24 if (pkList == null || pkList.Count == 0) 25 throw new ArgumentException("The Table entity have not a primary key."); 26 List<object> arguments = new List<object>(); 27 StringBuilder builder = new StringBuilder(); 28 29 foreach (var change in table) 30 { 31 if (pkList.Contains(change.Name)) 32 continue; 33 if (arguments.Count != 0) 34 builder.Append(", "); 35 builder.Append(change.Name + " = {" + arguments.Count + "}"); 36 if (change.PropertyType == typeof(string) || change.PropertyType == typeof(DateTime)) 37 arguments.Add("'" + change.GetValue(entity, null).ToString().Replace("'", "char(39)") + "'"); 38 else 39 arguments.Add(change.GetValue(entity, null)); 40 } 41 42 if (builder.Length == 0) 43 throw new Exception("沒有任何屬性進行更新"); 44 45 builder.Insert(0, " UPDATE " + string.Format("[{0}]", entityType.Name) + " SET "); 46 47 builder.Append(" WHERE "); 48 bool firstPrimaryKey = true; 49 50 foreach (var primaryField in pkList) 51 { 52 if (firstPrimaryKey) 53 firstPrimaryKey = false; 54 else 55 builder.Append(" AND "); 56 57 object val = entityType.GetProperty(primaryField).GetValue(entity, null); 58 builder.Append(GetEqualStatment(primaryField, arguments.Count)); 59 arguments.Add(val); 60 } 61 return new Tuple<string, object[]>(builder.ToString(), arguments.ToArray()); 62 63 }
而對子類公開的Update方法，我們進行了一個封裝，它通過操作枚舉來確實你是要insert,update還是delete，看代碼
1 /// <summary> 2 /// 執行ＳＱＬ，根據ＳＱＬ操作的類型 3 /// </summary> 4 /// <typeparam name="TEntity"></typeparam> 5 /// <param name="list"></param> 6 /// <param name="sqlType"></param> 7 /// <returns></returns> 8 protected string DoSQL<TEntity>(IEnumerable<TEntity> list, SQLType sqlType) where TEntity : class 9 { 10 StringBuilder sqlstr = new StringBuilder(); 11 switch (sqlType) 12 { 13 case SQLType.Insert: 14 list.ToList().ForEach(i => 15 { 16 Tuple<string, object[]> sql = CreateInsertSQL(i); 17 sqlstr.AppendFormat(sql.Item1, sql.Item2); 18 }); 19 break; 20 case SQLType.Update: 21 list.ToList().ForEach(i => 22 { 23 Tuple<string, object[]> sql = CreateUpdateSQL(i); 24 sqlstr.AppendFormat(sql.Item1, sql.Item2); 25 }); 26 break; 27 case SQLType.Delete: 28 list.ToList().ForEach(i => 29 { 30 Tuple<string, object[]> sql = CreateDeleteSQL(i); 31 sqlstr.AppendFormat(sql.Item1, sql.Item2); 32 }); 33 break; 34 default: 35 throw new ArgumentException("請輸入正確的參數"); 36 } 37 return sqlstr.ToString(); 38 }