我可以将以下内容重组为更紧凑的 linq 查询吗,理想情况下不引入辅助函数?
var revPerUnitChanges =
from row in this.DataTable.GetChanges(DataRowState.Modified).AsEnumerable()
let field = "Rev/Unit"
select new {
Field = field,
From = row.Field<decimal>(field, DataRowVersion.Original),
To = row.Field<decimal>(field, DataRowVersion.Current),
ItemIds = row.Field<string>("ItemIds"),};
var costPerUnitChanges =
from row in this.DataTable.GetChanges(DataRowState.Modified).AsEnumerable()
let field = "Cost/Unit"
select new {
Field = field,
From = row.Field<decimal>(field, DataRowVersion.Original),
To = row.Field<decimal>(field, DataRowVersion.Current),
ItemIds = row.Field<string>("ItemIds"), };
var numUnitsChanges =
from row in this.DataTable.GetChanges(DataRowState.Modified).AsEnumerable()
let field = "Units"
select new {
Field = field,
From = row.Field<decimal>(field, DataRowVersion.Original),
To = row.Field<decimal>(field, DataRowVersion.Current),
ItemIds = row.Field<string>("ItemIds"), };
var changes =
revPerUnitChanges
.Concat(costPerUnitChanges
.Concat(numUnitsChanges))
.Where(c => c.From != c.To);
首先创建一个帮助程序类来保存数据。 (您的代码使用匿名类型没有任何问题,但是如果您想将节重构为方法,使用命名类会容易得多。
public class MyClass //TODO give better name
{
public MyClass(DataRow row, string field) //You could have a public static generate method if it doesn't make sense for this to be a constructor.
{
Field = field;
From = row.Field<decimal>(field, DataRowVersion.Original);
To = row.Field<decimal>(field, DataRowVersion.Current);
ItemIds = row.Field<string>("ItemIds");
}
public string Field { get; set; }
public decimal From { get; set; }
public decimal To { get; set; }
public string ItemIds { get; set; }
}
现在我们已经解决了这个问题,查询就相当简单了。
var changes = dataTable.GetChanges(DataRowState.Modified)
.AsEnumerable()
.Select(row => new[]{ //create 3 new items for each row
new MyClass(row, "Rev/Unit"),
new MyClass(row, "Cost/Unit"),
new MyClass(row, "Units"),
})
.SelectMany(item => item) //flatten the inner array
.Where(item => item.From != item.To);