EF架构~过滤导航属性等，拼接SQL字符串

拼接Ｔ—ＳＱＬ串，并使它具有通用性

好处：与服务器建立一次连接，给服务器发一条ＳＱＬ命令，即可实现

代码如下：

 1   /// <summary>
 2         /// 构建Insert语句串
 3         /// 主键为自增时，如果主键值为0，我们将主键插入到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();//过滤主键，航行属性，状态属性等
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         }

对于EF架构中的批量更新操作，需要我们为实体的导航属性进行手动的标示，因为EF生成的实体中没有一个特殊的说明，所以，我们必须要告诉系统，哪个属性是导航属性，而导航属性是我们不去进行update的。

1    /// <summary>
2     /// 属性的导航属性
3     /// </summary>
4     public class NavigationAttribute : Attribute
5     {
6
7     }

而对于要进行批量更新的实体，我们需要为导航属性添加这个特性

1    public class User
2     {
3         public int UserID { get; set; }
4         [Navigation]
5         public User_Extension User_Extension { get; set; }
6     }

而对于我们构建批量Update语句，请看代码，它需要对导航属性进行过滤

 1         /// <summary>
 2         /// 构建Update语句串
 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)) //过滤导航属性
21                  ).ToArray();
22
23             //过滤主键，航行属性，状态属性等
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("没有任何属性进行更新");
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         }

而对子类公开的Update方法，我们进行了一个封装，它通过操作枚举来确实你是要insert,update还是delete，看代码

 1         /// <summary>
 2         /// 执行ＳＱＬ，根据ＳＱＬ操作的类型
 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("请输入正确的参数");
36             }
37             return sqlstr.ToString();
38         }

出处：http://www.cnblogs.com/lori/ 欢迎转载