c# - 如何在 LINQ 中的选择中添加 where 子句？

Question

我有以下内容：

var result =
    from entry in feed.Descendants(a + "entry")
    let content = entry.Element(a + "content")
    let properties = content.Element(m + "properties")
    let text = properties.Element(d + "Text")
    let title = properties.Element(d + "Title")
    let partitionKey = properties.Element(d + "PartitionKey")
    select new Content
    {
        Text = text.Value,
        Title = title.Value
    };

我想做的是添加一个位置，以便只有一些项目被放入结果中。如何添加条件：

partitionKey.Substring(2, 2) == "03" && text != null

选择？

Answer 1

代替

where partitionKey.Substring(2, 2) == "03" && text != null

利用

where partitionKey.Value.Substring(2, 2) == "03" && text != null

partitionKey 是 XElement 类型，当您需要它的值时。

Answer 2

只需在选择之前添加条件：

var result =
    from entry in feed.Descendants(a + "entry")
    let content = entry.Element(a + "content")
    let properties = content.Element(m + "properties")
    let text = properties.Element(d + "Text")
    let title = properties.Element(d + "Title")
    let partitionKey = properties.Element(d + "PartitionKey")
    where partitionKey.Value.Substring(2, 2) == "03"
    where text != null
    select new Content
    {
        Text = text.Value,
        Title = title.Value
    };

Answer 3

        var result =
from entry in feed.Descendants(a + "entry")
let content = entry.Element(a + "content")
let properties = content.Element(m + "properties")
let text = properties.Element(d + "Text")
let title = properties.Element(d + "Title")
let partitionKey = properties.Element(d + "PartitionKey")
where partitionKey.Value.Substring(2, 2) == "03" && text != null
select new Content
{
    Text = text.Value,
    Title = title.Value
};

Answer 4

在:where之前指定select

var result =
    from entry in feed.Descendants(a + "entry")
    let content = entry.Element(a + "content")
    let properties = content.Element(m + "properties")
    let text = properties.Element(d + "Text")
    let title = properties.Element(d + "Title")
    let partitionKey = properties.Element(d + "PartitionKey")
    where partitionKey.Substring(2, 2) == "03" && text != null
    select new Content
    {
        Text = text.Value,
        Title = title.Value
    };

Answer 5

我建议使用将 SQL 脚本转换为 LINQ 的 linquer 软件，在 Inner Joins 和更复杂的查询时想象一下？

访问：www.sqltolinq.com/

这是一个非常方便的工具！