如何在没有DataTables的情况下评估列表达式 [英] How to evaluate column expressions without DataTables
问题描述
我正在寻找一种方法来评估ADO.NET中可用的列表达式...而不使用DataTable实例。
I’m looking for a way to evaluate the column Expression available in ADO.NET … without using a DataTable instance.
假设我有一个像iif这样的列表达式(a> b,true,false)
Say I have a column expression like iif(a > b, true, false)
有没有办法通过传递a和b的某种方式来计算这个表达式?
Is there a way to evaluate this expression by passing somehow values for a and b?
我查看了DataTable上的 计算方法,但它并不是我想要的:
I looked at the Compute method on DataTable but it is not quite what I’m looking for:
object result1 = new DataTable()。Compute(" 20.0 / 2",null);
object result1 = new DataTable().Compute("20.0 / 2", null);
object result3 = new DataTable()。Compute(" iif(10> 5,true,false)",null);
object result3 = new DataTable().Compute("iif(10 > 5, true, false)", null);
object result2 = new DataTable()。Compute(" iif(a> b,true,false)",null); - 如何评估这个
object result2 = new DataTable().Compute("iif(a > b, true, false)", null); -- how to evaluate this
这背后的想法是出于性能原因从DataTable转移到简单的数组结构。
Idea behind this is to move away from DataTable to simple array structure for performance reason.
我还需要支持一种生成使用的遗留表达式的方法。
Still I need to support a way to generate the legacy expression used.
我宁愿避免构建表达式字符串来生成它,因为对于大量行来说它的性能会很差。
I would rather avoid building the expression string to generate this as it will be poor performance for large number of rows.
预先感谢您的帮助
Nick
推荐答案
如果表达式是预定义的,那么你可以写
a = ...
b = ...
result2 = a> b;
a = …
b = …
result2 = a > b;
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