// 不优化的情况:每次都创建新的 StringBuilder
for (int i = 0; i < 1000; i++)
{var builder = new StringBuilder();builder.Append("Number: ");builder.Append(i);Console.WriteLine(builder.ToString());
}// 优化后的情况:重用同一个 StringBuilder
var sharedBuilder = new StringBuilder();
for (int i = 0; i < 1000; i++)
{sharedBuilder.Clear();sharedBuilder.Append("Number: ");sharedBuilder.Append(i);Console.WriteLine(sharedBuilder.ToString());
}