Question

我有以下LINQ查询。要检入传入值为null，我使用?（例如：<decimal?>）。即使值为null，这也允许查询继续。但是，如何返回0，而不是返回空值？我在我的代码中使用下游的这些值，如果为null，则抛出错误。

var query = referenceDt.AsEnumerable()
    .Where(results => comp(results.Field<decimal?>("OFR_Percent"), ofrPercent) &&
                      results.Field<int?>("ComputeEmptyNodeCount") <= nodeCount)
    .OrderBy(results => results.Field<string>("Cluster"))
    .Select(results => new
    {
        ServerGroup= results.Field<string>("Cluster"),
        OOS_Percent = results.Field<decimal?>("OOS_Percent"),
        OutOfServiceCores = results.Field<int?>("OutOfServiceCores"),
        OFR_Percent = results.Field<decimal>("OFR_Percent"),
        OFR_Count = results.Field<int>("OutForRepairNodeCount"),
        RawTotalNodes = results.Field<int>("RawTotalNodes")
    });

Answer 1

您可以使用null-coalescing operator（??）运算符。如果它不为null，则返回左操作数，否则返回右操作数。

.Select(results => new
{
    ServerGroup= results.Field<string>("Cluster") ?? "",
    OOS_Percent = results.Field<decimal?>("OOS_Percent")?? 0,
    OutOfServiceCores = results.Field<int?>("OutOfServiceCores") ?? 0,
    OFR_Percent = results.Field<decimal>("OFR_Percent"),
    OFR_Count = results.Field<int>("OutForRepairNodeCount"),
    RawTotalNodes = results.Field<int>("RawTotalNodes")
});

LINQ Null返回0

1 个答案: