string的操作可以试下下面的string yourStr = " a1, a2, a3,...a11, a12..."
string resultStr = yourStr;
if (yourStr.IndexOf(",") > -1)
{
resultStr = " A" + yourStr.Substring(yourStr.IndexOf(","));
}用正则的这样试下string yourStr = " a1, a2, a3,...a11, a12..."
string reStr = "A";
string resultStr = Regex.Replace(yourStr, @"(\s*?)\S+(\s*?,[\s\S]*?$)", @"$1"+reStr+"$2", RegexOptions.IgnoreCase);
string resultStr = yourStr;
if (yourStr.IndexOf(",") > -1)
{
resultStr = " A" + yourStr.Substring(yourStr.IndexOf(","));
}用正则的这样试下string yourStr = " a1, a2, a3,...a11, a12..."
string reStr = "A";
string resultStr = Regex.Replace(yourStr, @"(\s*?)\S+(\s*?,[\s\S]*?$)", @"$1"+reStr+"$2", RegexOptions.IgnoreCase);
string yourStr = " a1, a2, a3,...a11, a12..., a1,....,a123,...";
string resultStr = Regex.Replace(yourStr, @"\ba1\b", @"A");
string result;
string yourStr = " a1, a2, a3,...a11, a12..., a1,....,a123,...";
result = yourStr.Replace("a1,", "A,");
或者 result = Regex.Replace(yourStr, @"\ba1\b", @"A");
楼上两位的方法都可以实现或者只将第一个出现的a1替换掉int index=yourStr.IndexOf("a1,");
result = yourStr.Remove(index, "a1".Length).Insert(index, "A");