分享自己做的一个简单的查询表达式模拟（ESQL,Linq)(1)

完全的模拟表达式非常困难，因为C#目前不支持自定义操作符，只支持操作符重载（希望C#能够提供操作符自定义，如果有语言支持这个，也请告知），思路其实很简单，就是建立自己的类型，并重载一些操作符，模拟这个的目的就是在实体模型下规避直接写数据库SQL语句，用类似于ESQL,Linq语法完成这个工作，提供开发一个一致的实体应用模型：
1）参数类，用于传递实际参数，最终转换成ADO.Net的命令中需要的参数：
[csharp]
public class Parameter 
    {//没有具体实现，这里只需要模拟 
    } 
2)表达式接口：
[csharp]
public inte易做图ce IDbExpression 
    { 
        string Expression { get; } 
        Dictionary<string, Parameter> Parameters {get;} 
    } 
3)表达式基类：主要是一些操作符号重载，一些无法用表达式的地方定义类似的函数
[csharp]
public class DbExpression : IDbExpression 
    { 
        private StringBuilder _sqlStatement; 
        private  Dictionary<string, Parameter> _Parameters; 
        public StringBuilder SQL { get { return _sqlStatement; } } 
        public DbExpression() 
        { 
            _sqlStatement = new StringBuilder(); 
            _Parameters = new Dictionary<string, Parameter>(); 
        } 
        public static DbExpression operator >(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " > " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp;  
        } 
        public static DbExpression operator <(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " < " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator >=(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " >= " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator <=(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " <= " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator ==(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " = " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator !=(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " != " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator &(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " and " + e2.Expression); 
            theExp.AddParams(e1); 
            theExp.AddParams(e2); 
            return theExp; 
        } 
        public static DbExpression operator |(DbExpression e1, DbExpression e2) 
        { 
            DbExpression theExp = new DbExpression(); 
            theExp.SQL.AppendLine(e1.Expression + " or " + e2.Expression); 
  

补充：软件开发 , C# ,