正则表达式 – VB.Net删除第三个连字符后的所有内容

string test = "170-0175-00B-BEARING PLATE MACHINING.asm:2";
int num = 2;
int index = test.IndexOf('-');
while(index > 0 && num > 0)
{
    index = test.IndexOf('-',index+1);
    num--;
}
if(index > 0)
    test = test.Substring(0,index);

当然,如果你要搜索最后一个连字符,那么更简单

int index = test.LastIndexOf('-');
if(index > 0)
    test = test.Substring(0,index);