字符串格式:删除最后一个下划线和以下字符

var data = new List<string> {"A_1", "A_2", "A_B_1", "X_a_Z_14"};

int trimPosition;
for (var i = 0; i < data.Count; i++)
         if ((trimPosition = data[i].LastIndexOf('_')) > -1)
            data[i] = data[i].Substring(0, trimPosition);

string[] names = {"A_1","A_2","A_B_1","X_a_Z_14" };
for (int i = 0; i < names.Length;i++ )
   names[i]= names[i].Substring(0, names[i].LastIndexOf('_'));

var s = "X_a_Z_14";
var result = s.Substring(0, s.LastIndexOf('_') ); // X_a_Z

string s = "X_a_Z_14";

s = s.Substring(0, s.LastIndexOf("_"));

input.Substring(0,input.LastIndexOf("_"));

如果您愿意,也可以使用正则表达式。

Regex regex = new Regex("_[^_]*$");
string[] strings = new string[] {"A_1", "A_2", "A_B_1", "X_a_Z_14"};
foreach (string s in strings)
{
    Console.WriteLine(regex.Replace(s, ""));
}