linq 表达式树的构建 Expression.Lambda

遇到个问题

http://topic.csdn.net/u/20100419/11/0fd531ee-3ecb-4c82-a75e-d06c392202db.html?1713776579

解决方法

http://topic.csdn.net/u/20100413/17/88bb3a5f-fe4e-4370-851c-7a007a781653.html

 

ParameterExpression numParam = Expression.Parameter(typeof(string), "str");
        ConstantExpression b = Expression.Constant(true, typeof(bool));
        MethodCallExpression methodCall = Expression.Call(typeof(string).GetMethod("IsNullOrEmpty"), numParam);
        BinaryExpression isEqual = Expression.NotEqual(methodCall, b);
        Expression<Func<string, bool>> lambda1 =
            Expression.Lambda<Func<string, bool>>(
                isEqual,
                new ParameterExpression[] { numParam });


对应的Lambel 是 

C# code

str => string.IsNullOrEmpty(str)!=true

===================================================================
ParameterExpression strParam = Expression.Parameter(typeof(string), "str");

        MethodInfo cMe = typeof(string).GetMethod("Contains");

        ConstantExpression ce = Expression.Constant("a",typeof(string));

        MethodCallExpression call = Expression.Call(strParam, cMe, ce);

        Expression<Func<string, bool>> lam = Expression.Lambda<Func<string, bool>>(call, strParam);
随笔