如何使用 String.IndexOf 方法找到正确的值？

Question

我想让我的句子如下所示，但是如何使用 String.IndexOf 方法找到正确的 MINVALUE 值，以便在给定条件下从句子中的值变化开始？

句子

CREATE SEQUENCE "MY_TEST_SEQUENCE" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH 55 CACHE 20 NOORDER NOCYCLE

结果

CREATE SEQUENCE "MY_TEST_SEQUENCE" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH 8 CACHE 20 NOORDER NOCYCLE

条件

1. 如果 MINVALUE 的值为正值 (8)，则开始时的值与 最小值 (8)...
2. 如果 MINVALUE 具有负 (-8) 值而不是从与 MAXVALUE (999) 相同的值开始

我的代码

var startvalue = 0;
if(MINVALUE > 0)
{
    startvalue = MINVALUE;
}
Else if(MINVALUE < 0)
{
    startvalue = MAXVALUE;
}
var result = String.Format(@"CREATE SEQUENCE ""MY_TEST_SEQUENCE"" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH {0}  CACHE 20 NOORDER NOCYCLE",startvalue)

Answer 1

我认为这应该适合你；

string sentence = @"CREATE SEQUENCE 'MY_TEST_SEQUENCE' MINVALUE -8 MAXVALUE 999 INCREMENT BY 1 START WITH 55 CACHE 20 NOORDER NOCYCLE";
string pattern = @".*\s+MINVALUE[ ]*(?<MinValue>[-?\d]*)[ ]*MAXVALUE[ ]*(?<MaxValue>[\d]*)";
Regex rgx = new Regex(pattern);
Match match = rgx.Match(sentence);
Group gp1 = match.Groups[1];//-8 or 8 (both valid).
Group gp2 = match.Groups[2];//Value after MAXVALUE.
if (gp1.Value.StartsWith("-") == false)//No minus sign,that must be a positive value.
{
  string s2 = string.Format(@"CREATE SEQUENCE ""MY_TEST_SEQUENCE"" MINVALUE 8 MAXVALUE 999  INCREMENT BY 1 START WITH {0} CACHE 20 NOORDER NOCYCLE", gp1.Value);
  MessageBox.Show(s2);
}

else if (gp1.Value.StartsWith("-") == true)//No need for further checking, a value with - will always be smaller.
{
  string s2 = string.Format(@"CREATE SEQUENCE ""MY_TEST_SEQUENCE"" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH {0} CACHE 20 NOORDER NOCYCLE", gp2.Value);
  MessageBox.Show(s2);
}

Answer 2

似乎带有捕获组的正则表达式比尝试将字符串分解成片段更合适。

var regex = new Regex(@".*\s+MINVALUE\s+(-?\d*)\s+MAXVALUE\s+(-?\d*)\s+.*");
var sentence = @"CREATE SEQUENCE ""MY_TEST_SEQUENCE"" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH 55 CACHE 20 NOORDER NOCYCLE";

var match = regex.Match(sentence);

if (match.Groups.Count != 3)
{
    throw new ApplicationException("input string not in expected format");
}

var minValue = int.Parse(match.Groups[1].Value);
var maxValue = int.Parse(match.Groups[2].Value);

var result = string.Format(@"CREATE SEQUENCE ""MY_TEST_SEQUENCE"" MINVALUE 8 MAXVALUE 999 INCREMENT BY 1 START WITH {0}  CACHE 20 NOORDER NOCYCLE", minValue < 0 ? maxValue : minValue);