分享自己做的一个简单的查询表达式模拟(ESQL,Linq)(2)
2012-02-11 08:31 java线程例子 阅读(164) 评论(0) 编辑 收藏 举报下面是几个特殊化的表达式类:
4)常量表达式:
public class ConstExp<T> : DbExpression { public string ParamName { get; private set; } public T Value { get; private set; } public ConstExp(T Value, string ParamName) : base() { this.Parameters.Add(ParamName, new Parameter() { }); this.Value = Value; this.ParamName = ParamName; } public override string Expression { get { return ":"+this.ParamName; } } public static ConstExp<T> C(string ParamName, T V) { return new ConstExp<T>(V, ParamName); } }
5)实体表信息表达式:
public class TableInfo : IDbExpression { public string TableName{get;set;} public string Expression { get {return TableName;} } public virtual Dictionary<string, Parameter> Parameters { get { return null; } } }
6)实体字段信息表达式:
public class FieldInfo : IDbExpression { public string FieldName{get;set;} public string Expression { get { return FieldName; } } public virtual Dictionary<string, Parameter> Parameters { get { return null; } } public static FieldInfo All { get { return new FieldInfo() { FieldName= "*" }; } } }
7)别名表达式
public class AliasExp : DbExpression { public AliasExp(string AliasName) { this.AliasName = AliasName; } public string AliasName { get;private set; } public override string Expression { get { return "AliasName"; } } public override Dictionary<string, Parameter> Parameters { get { return null; } } public static readonly AliasExp T1; public static readonly AliasExp T2; public static readonly AliasExp T3; public static readonly AliasExp T4; public static readonly AliasExp T5; public static readonly AliasExp T6; public static readonly AliasExp T7; public static readonly AliasExp T8; public static readonly AliasExp T9; public static readonly AliasExp A1; public static readonly AliasExp A2; public static readonly AliasExp A3; public static readonly AliasExp A4; public static readonly AliasExp A5; public static readonly AliasExp A6; static AliasExp() { T1 = new AliasExp("T1"); T2 = new AliasExp("T2"); T3 = new AliasExp("T3"); T4 = new AliasExp("T4"); T5 = new AliasExp("T5"); T6 = new AliasExp("T6"); T7 = new AliasExp("T7"); T8 = new AliasExp("T8"); T9 = new AliasExp("T9"); A1 = new AliasExp("A1"); A2 = new AliasExp("A2"); A3 = new AliasExp("A3"); A4 = new AliasExp("A4"); A5 = new AliasExp("A5"); A6 = new AliasExp("A6"); } public DbExpression this[FieldInfo e] { get { DbExpression theExp = new DbExpression(); theExp.SQL.Append(this.AliasName + "." + e.Expression); theExp.AddParams(e); return theExp; } } public DbExpression this[TableInfo e] { get { DbExpression theExp = new DbExpression(); theExp.SQL.Append(e.Expression + " " + this.AliasName); theExp.AddParams(e); return theExp; } } public DbExpression this[DbExpression e] { get { DbExpression theExp = new DbExpression(); theExp.SQL.Append(e.Expression + " " + this.AliasName); theExp.AddParams(e); return theExp; } } }