//有三个文本框，手动输入数据
var data1 = textbox1.Text;
var data2 = textbox2.Text;
var data3 = textbox3.Text;

 Func<string, bool> Filter1 = x => x.Any(y => data1.Contains(y));
 Func<string, bool> Filter2 = x => x.Any(y => data2.Contains(y));
 Func<string, bool> Filter3 = x => x.Any(y => data3.Contains(y));
//如果文本框不为空，单独一个文本框输入对应的输出分别为：
//第一个文本框
var result = Enumerable.Range(0, 1000).Where(x => Filter1(x.ToString().PadLeft(3, '0')));
//第二个文本框
var result = Enumerable.Range(0, 1000).Where(x => Filter2(x.ToString().PadLeft(3, '0')));
//第三个文本框
var result = Enumerable.Range(0, 1000).Where(x => Filter3(x.ToString().PadLeft(3, '0')));
//如果三个文本框都有数据输入，则输出result为上述三个输出的交集
Func<string, bool> Filter = x => true;
Filter = x => Filter1(x) && Filter2(x) && Filter3(x);
var result = Enumerable.Range(0, 1000).Where(x => Filter(x.ToString().PadLeft(3, '0')));

//如果三个文本框有空的情况，上述的result输出就会为空，这个时候需要判断哪几个文本框输入不为空，对输入不为空的文本框输出进行交集处理，此时如果仅仅只有三个文本框，则用If判断后组合交集也比较方便，但是效率低
//如果有N个文本框，对应上述类似情况，该怎么改？

Func<string, bool> Filter1 = x => string.IsNullOrEmpty(data1) || x.Any(y => data1.Contains(y));
Func<string, bool> Filter2 = x => string.IsNullOrEmpty(data2) || x.Any(y => data2.Contains(y));
Func<string, bool> Filter3 = x => string.IsNullOrEmpty(data3) || x.Any(y => data3.Contains(y));