如何使用条件

Question

我们可以动态地在linq查询上的条件中放置吗？

例如:

class Result
{
      string v1;
      string v2;
      string v3;
}

List<Result> result = (from r in results select r);


//i want to do something like the following....

if(conditionA)
{
    result = result appened (or v1 = xxx)
}
else if(conditionB)
{
    result = result appened (or v2 = xxx)
}
else if(conditionC)
{
    result = result appened (or v3 == xxx)
}

任何人都知道如何处理Linq的情况????

钍

Answer 1

对于and子句的关系，您可以轻松地附加.Where()过滤方法，如下所示：

where conditionOriginal(r) and conditionDynamic(r)

作为

var results = (from r in originalResults
               where originalConditions(r)
               select r);
...
if (conditionA)
    results = results.Where(r => conditionDynamic(r));

但是，要附加“或”类型关系，您必须与原始结果集联合，如下所示：

where conditionOriginal(r) or conditionDynamic(r)

变成

var results = (from r in originalResults
               where conditionOriginal(r)
               select r);
...
if (conditionB)
    results = results.Union((from r in originalResults
                             where conditionDynamic(r)
                             select r));

或者

if (conditionB)
    results = results.Union(originalResults.Where(conditionDynamic(r)));