asp.net 数组中字符串替换的几种方式

//方法1
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
ReplaceStr();
}
}
public void ReplaceStr()
{
ArrayList MyArray = new ArrayList();
MyArray.Add("123");
MyArray.Add("aaa");
if (MyArray.Contains("aaa"))
{
MyArray.Remove("aaa");
MyArray.Add("bbb");
}
for (int i = 0; i <= MyArray.Count - 1; i++)
{
Response.Write(MyArray[i].ToString());
}
}

//方法2
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
ReplaceStr();
}
}
public void ReplaceStr()
{
string [] tm = new string[] { "123", "aaa" };
for (int i = 0; i < tm.Length; i++)
{
if (tm[i].ToString() == "aaa")
{
tm[i]=tm[i].Replace("aaa", "bbb");

}
}
for (int i = 0; i <= tm.Length - 1; i++)
{
Response.Write(tm[i].ToString());
}
}
//方法3
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string[] tm = new string[] { "123", "aaa" };
string Array=ReplaceValue(tm, "aaa", "bbb", ",");
Response.Write(Array);
}
}
public static string ReplaceValue(string[] item, string oldSv, string newSv, string separator)
{
if (item == null) return string.Empty;
StringBuilder sb = new StringBuilder();
foreach (string s in item)
{
if (s == oldSv)
{
sb.Append(newSv);
sb.Append(separator);
}
else
{
sb.Append(s);
sb.Append(separator);
}
}
string returnstr = sb.ToString();
returnstr = (returnstr.EndsWith(separator)) ? returnstr.Substring(0, returnstr.Length - 1) : returnstr;
return returnstr;
}