从this link我可以动态创建一个Expression <Func <T,bool >>谓词
这段代码可以动态创建s => s.Id == 1
ParameterExpression argParam = Expression.Parameter(typeof(User), "s");
var propertyExp = Expression.Property(parameterExp, "Id");
var constExp = Expression.Constant(1);
var body = Expression.Equal(propertyExp, constExp);
var lambda = Expression.Lambda<Func<User, bool>>(body, parameterExp);
但是如何创建Expression <Func <T1,T2,bool >>和Expression <Func <T1,T2,T3,bool >>
如何动态创建如下:(a,b)=> a.Id == 1 && b.Name ==“name”
Func<T, bool>
和Func<T1, T2, bool>
之间的区别在于第二个接受两个参数,因此您需要使用Expression.Parameter
创建两个参数。
下面的代码将创建一个表达式
(t1,t2)=> t1.Id == 1 && t2.Name == name;
private static Expression<Func<T1, T2, bool>> CreateExpression<T1, T2>()
{
var t1 = Expression.Parameter(typeof(T1), "t1");
var t2 = Expression.Parameter(typeof(T2), "t2");
var idProp = Expression.PropertyOrField(t1, "Id");
var nameProp = Expression.PropertyOrField(t2, "Name");
var body = Expression.AndAlso(
Expression.Equal(idProp, Expression.Constant(1)),
Expression.Equal(nameProp, Expression.Constant("name"))
);
var lambda = Expression.Lambda<Func<T1, T2, bool>>(body, t1, t2);
return lambda;
}