方法在LINQ查询中调用两次

在我们的应用程序中，我们有一个如下的小查询：

var selectedAgents = from agent in listAgents
    where (this.collectionVehicles.GetVehicleByAgent(agent)).IsActive || 
          (this.collectionVehicles.GetVehicleByAgent(agent)).IsSoldSinceCurrentSession 
           select agent;

Vehicle parentVehicle = collectionVehicles.GetVehicleByAgent(agent);

if (parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession)
{
    selectedAgents.Add(agent);
}

var selectedAgents =
    from agent in listAgents
    let parentVehicle = collectionVehicles.GetVehicleByAgent(agent)
    where parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession 
    select agent;

这很好，但是getVehicleBayAgent方法被调用了两次，这可能不是必需的

在LINQ之前，我们有一个foreach循环，并这样做：

var selectedAgents = from agent in listAgents
    where (this.collectionVehicles.GetVehicleByAgent(agent)).IsActive || 
          (this.collectionVehicles.GetVehicleByAgent(agent)).IsSoldSinceCurrentSession 
           select agent;

Vehicle parentVehicle = collectionVehicles.GetVehicleByAgent(agent);

if (parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession)
{
    selectedAgents.Add(agent);
}

var selectedAgents =
    from agent in listAgents
    let parentVehicle = collectionVehicles.GetVehicleByAgent(agent)
    where parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession 
    select agent;

正如您所看到的，GetVehicleBayAgent返回一个Vehicle对象，可以轻松地进行多次比较。因此，我正在寻找一种方法，在LINQ查询中重新设置车辆并保留它。我不想调用GetVehicleBayAgent两次。

您需要使用，如下所示：

var selectedAgents = from agent in listAgents
    where (this.collectionVehicles.GetVehicleByAgent(agent)).IsActive || 
          (this.collectionVehicles.GetVehicleByAgent(agent)).IsSoldSinceCurrentSession 
           select agent;

Vehicle parentVehicle = collectionVehicles.GetVehicleByAgent(agent);

if (parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession)
{
    selectedAgents.Add(agent);
}

var selectedAgents =
    from agent in listAgents
    let parentVehicle = collectionVehicles.GetVehicleByAgent(agent)
    where parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession 
    select agent;

您需要使用，如下所示：

var selectedAgents = from agent in listAgents
    where (this.collectionVehicles.GetVehicleByAgent(agent)).IsActive || 
          (this.collectionVehicles.GetVehicleByAgent(agent)).IsSoldSinceCurrentSession 
           select agent;

Vehicle parentVehicle = collectionVehicles.GetVehicleByAgent(agent);

if (parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession)
{
    selectedAgents.Add(agent);
}

var selectedAgents =
    from agent in listAgents
    let parentVehicle = collectionVehicles.GetVehicleByAgent(agent)
    where parentVehicle.IsActive || parentVehicle.IsSoldSinceCurrentSession 
    select agent;

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是的，就是这样！工作完美！是的，就是这样！工作完美！