c# - .Net Core C# - LINQ 查询运算符可以按逻辑分隔吗？

Question

假设我有六个 LINQ 查询。每个查询都包含前一个查询使用的运算符，并向链中添加一个运算符:

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
 )
 .ToListAsync(); 

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        .Where(f => f.recordid == x)
 )
 .ToListAsync(); 

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        .Where(f => f.recordid == x)
        .Where(f => !StatusExceptionList.Contains(r.Status))
 )
 .ToListAsync(); 

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        .Where(f => f.recordid == x)
        .Where(f => !StatusExceptionList.Contains(r.Status))
        .OrderBy(f => f.date1)
 )
 .ToListAsync(); 

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        .Where(f => f.recordid == x)
        .Where(f => !StatusExceptionList.Contains(r.Status))
        .OrderBy(f => f.date1)
        .ThenBy(f => f.date2)
)
.ToListAsync(); 

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        .Where(f => f.recordid == x)
        .Where(f => !StatusExceptionList.Contains(r.Status))
        .OrderBy(f => f.date1)
        .ThenBy(f => f.date2)
        .ThenBy(f => f.recordid)
)
.ToListAsync(); 

我想将其压缩为一个查询，并在不同的 linq 运算符之间交织逻辑，如该伪代码所示，但这根本行不通。我四处搜索，不确定接下来要尝试什么:

Foo = await
(
    _context.Foo
        .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31)
        if (some logic)
        {
            .Where(f => f.recordid == x)
        }
        if (some different logic)
        {           
            .Where(f => !StatusExceptionList.Contains(r.Status))
        }
        if (some different logic)
        {
            .OrderBy(f => f.date1)
        }
        if (some different logic)
        {
            .ThenBy(f => f.date2)
        }
        if (some different logic)
        {
            .ThenBy(f => f.recordid)
        }
)
.ToListAsync(); 

谁能给我指出正确的方向，或者告诉我我是否试图以错误的方式解决这个问题？非常感谢!!!

Answer 1

只需将查询存储在单独的变量中:

IQueryable<Foo> query = _context.Foo
    .Where(f => (Convert.ToDateTime(f.date1) - today).TotalDays < 31);

然后附加您的支票:

if (someCondition) {
    query = query.Where(f.recordid == x);
}

等等。最后 - 运行查询:

Foo = await query.ToListAsync();

使用 OrderBy 和 ThenBy - 检查查询是否已经是 IOrderedQueryable:

if (someCondition) {
    var ordered = query as IOrderedQueryable<Foo>;
    if (ordered != null)
        query = ordered.ThenBy(x => x.field);
    else 
        query = query.OrderBy(x => x.field);
}