如何手动构建将始终返回true的Expression？

Question

我试图创建Expression,但失败了.

我想建立类似的东西 Expression<Func<typeof(type), bool>> expression = _ => true;

我的尝试:

private static Expression GetTrueExpression(Type type)
{
    LabelTarget returnTarget = Expression.Label(typeof(bool));
    ParameterExpression parameter = Expression.Parameter(type, "x");

    var resultExpression = 
      Expression.Return(returnTarget, Expression.Constant(true), typeof(bool));

    var delegateType = typeof(Func<,>).MakeGenericType(type, typeof(bool));

    return Expression.Lambda(delegateType, resultExpression, parameter); ;
}

用法:

var predicate = Expression.Lambda(GetTrueExpression(typeof(bool))).Compile();

但是我收到了错误: Cannot jump to undefined label ''

Answer 1

就如此容易:

private static Expression GetTrueExpression(Type type)
{
    return Expression.Lambda(Expression.Constant(true), Expression.Parameter(type, "_"));
}