字段掩码

在 Google Ads API 中，字段掩码用于提供 API 请求应更新的字段列表。即使发送到服务器，系统也会忽略字段掩码中未指定的任何字段。

FieldMasks 类

在 .NET 客户端库中生成字段掩码的推荐方法是使用内置的 FieldMasks 实用程序类，该类可让您从修改后的对象生成字段掩码，而无需从头开始构建。

以下示例展示了如何更新广告系列，其中使用 FieldMasks.AllSetFieldsOf 方法生成一个枚举所有已设置字段的字段掩码。然后，您可以将生成的字段掩码直接传递给更新调用：

// Update campaign by setting its status to paused, and "Search network" to
// false.
Campaign campaignToUpdate = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    Status = CampaignStatus.Paused,
    NetworkSettings = new NetworkSettings()
    {
        TargetSearchNetwork = false
    }
};

// Create the operation.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaignToUpdate,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaignToUpdate)
};

// Update the campaign.
MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });

有时，您可能需要处理现有对象并更新几个字段。在这种情况下，请改用 FieldMasks.FromChanges 方法。此方法会生成一个字段掩码，用于表示两个对象之间的差异：

Campaign existingCampaign;

// Obtain existingCampaign from an earlier API call.

// Create a new campaign based on the existing campaign for update.
Campaign campaignToUpdate = new Campaign(existingCampaign);

// Update campaign by setting its status to paused, and "Search network" to
// false.
campaignToUpdate.Status = CampaignStatus.Paused;
campaignToUpdate.NetworkSettings = new NetworkSettings()
{
    TargetSearchNetwork = false
};

// Create the operation.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaignToUpdate,
    UpdateMask = FieldMasks.FromChanges(existingCampaign, campaignToUpdate)
};

处理 FieldMaskError.FIELD_HAS_SUBFIELDS 错误

在极少数情况下，您可能需要设置某个消息字段，而不更新其任何子字段。请参考以下示例：

// Creates a campaign with the proper resource name and an empty
// MaximizeConversions field.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    MaximizeConversions = new MaximizeConversions()
};

CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaign)
};

MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });

此 API 调用失败，并显示 FieldMaskError.FIELD_HAS_SUBFIELDS 错误。由于 MaximizeConversions 具有子字段，因此 Google Ads API 服务器会要求请求中包含可变子字段的字段掩码。不过，在这种情况下，FieldMasks 无法自动生成子字段掩码，因为请求未设置任何子字段。

在这种情况下，您可以手动向 fieldMask.Paths（即 RepeatedField<string>）添加路径：

// Creates a Campaign object with the proper resource name.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
};

FieldMask fieldMask = FieldMasks.AllSetFieldsOf(campaign);
// Only include 'maximize_conversions.target_cpa_micros' in the field mask
// as it is the only mutable subfield on MaximizeConversions when used as a
// standard bidding strategy.
//
// Learn more about standard and portfolio bidding strategies at:
// https://developers.google.com/google-ads/api/docs/campaigns/bidding/assign-strategies
fieldMask.Paths.Add("maximize_conversions.target_cpa_micros");

// Creates an operation to update the campaign with the specified fields.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = fieldMask
};

清除字段

Google Ads API 支持清除某些字段值。如需清除某个字段，您必须手动将该字段纳入字段掩盖中，同时将资源对象中的该字段保持未设置状态。将字段设置为其默认值（例如 int64 字段的 0）不会清除该字段。

以下代码示例展示了如何清除 MaximizeConversions 出价策略的 target_cpa_micros 字段：

正确代码

以下代码会清除 target_cpa_micros 字段，因为它会将 maximize_conversions.target_cpa_micros 添加到字段掩码，而不会设置 campaign.MaximizeConversions.TargetCpaMicros 属性：

// Creates a Campaign object with the proper resource name.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
};

// Constructs a field mask from the existing campaign and adds the
// 'maximize_conversions.target_cpa_micros' field to the field mask, which
// clears this field from the bidding strategy without impacting any other
// fields on the bidding strategy.
FieldMask fieldMask = FieldMasks.AllSetFieldsOf(campaign);
fieldMask.Paths.Add("maximize_conversions.target_cpa_micros");

// Creates an operation to update the campaign with the specified field.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = fieldMask
};

验证码不正确

以下代码不会清除 target_cpa_micros 字段，因为它将该字段设置为 0。当 TargetCpaMicros 为 0 或从掩码中省略路径时，FieldMasks 实用程序和 Google Ads API 服务器都会忽略此值，并且服务器不会返回错误：

// Creates a campaign with the proper resource name and a
// MaximizeConversions object. Attempts to clear the target_cpa_micros
// field by setting it to 0.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    MaximizeConversions = new MaximizeConversions()
    {
        TargetCpaMicros = 0
    }
};

// Constructs an operation using FieldMasks.AllSetFieldsOf to derive the
// update mask.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaign)
};

// Sends the operation in a mutate request that succeeds without clearing
// the previous 'target_cpa_micros' value cleanly.
MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });