如何使用LINQ在字段中插入序号?

本文关键字：插入 字段 何使用 LINQ | 更新日期: 2023-09-27 18:06:15

我有以下代码，我使用实体框架将数据放入关系表:

    public IList<Objective> createObjectives()
    {
        var objectiveNames = new[]
        {
            "Objective 1",
            "Objective 2",
            "Objective 3",
            "Objective 4",
            "Objective 5",
            "Objective 6",
            "Objective 7",
            "Objective 8"
        };
        var objectives = objectiveNames.Select(o => new Objective
        {
            ObjectiveSeq = ??,
            Name = o,
            Description = o + " Description",
            ModifiedDate = DateTime.Now
        }
        );
        return objectives.ToList();
    }

我有一个新的字段在我的表名称ObjectiveSeq。我如何修改我的LINQ插入一个序列号在该字段从1开始。

如何使用LINQ在字段中插入序号?

 var objectives = objectiveNames.Select((o, index) => new Objective
        {
            ObjectiveSeq = index,
            Name = o,
            Description = o + " Description",
            ModifiedDate = DateTime.Now
        }
        );

Select函数有过载。你可以在这里找到。

Enumerable.Select<TSource, TResult> Method (IEnumerable<TSource>, Func<TSource, Int32, TResult>)

查看该页中显示的示例。

 string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };
 var query = fruits.Select((fruit, index) => new { index, str = fruit });
 foreach (var obj in query)
 {
    Console.WriteLine("{0}", obj);
 }

你可以看到我们正在使用(fruit, index)。您正在选择元素和索引。

输出将是

{ index = 0, str = apple }
{ index = 1, str = banana }
{ index = 2, str = mango }
{ index = 3, str = orange }
{ index = 4, str = passionfruit }
{ index = 5, str = grape }
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