LINQ to Db4O查询的条件子句? [英] Conditional clauses for linq to Db4O query?

问题描述

在linq to sql中，我可以这样:

In linq to sql i can do like this:

var q = db.Colors;
if(! string.IsNullOrEmpty(colorName))
   q = q.Where(c=>c.Name.Equals(colorName));
return q.ToList();

在Db4O linq中，我无法做到这一点，因为我必须先入手

In Db4O linq I can't do it like this because I have to start with

var q = (from Color c in db
         select c);
if(! string.IsNullOrEmpty(colorName))
   q = q.Where(c=>c.Name.Equals(colorName));
return q.ToList();

这将导致

1. 所有颜色的完整枚举
2. 按名称过滤.

这不是我旨在偏离目标的解决方案. 有什么建议吗?

That's not the solution I was aiming for off course. Any suggestions?

推荐答案

像这样的东西适合吗?

return (from Color c in db
       where !String.IsNullOrEmpty(colorName) && c.Name.Equals(colorName)
       select c).ToList();

然后，您还可以使用多个参数:

You can then also use multiple parameters:

return (from Color c in db
       where (!String.IsNullOrEmpty(colorName) && c.Name.Equals(colorName))
          || (!String.IsNullOrEmpty(color1Name) && c.Name.Equals(color1Name))
          || (!String.IsNullOrEmpty(color2Name) && c.Name.Equals(color2Name))
          ...
       select c).ToList();

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