Question

我有一个带有四个列的DataGridView，需要从其内容中创建一个多行字符串，用逗号分隔。
这段代码可行，但可能 - 有一种更优雅的方式：

string multiLine = "";
string singleLine;    
foreach (DataGridViewRow r in dgvSm.Rows)
{
    if (!r.IsNewRow)
    {
        singleLine = r.Cells[0].Value.ToString() + ","
        + r.Cells[1].Value.ToString() + ","
        + r.Cells[2].Value.ToString() + ","
        + r.Cells[3].Value.ToString() + Environment.NewLine;
        multiLine = multiLine + singleLine;
    }
}

Answer 1

我不知道优雅，但是：

使用StringBuilder 进行字符串操作，类型字符串是不可变的！
如果您需要在两者之间执行某些操作，请将第一个或最后一个循环分开（例如逗号分隔）所以，基本上是这样的：

StringBuilder multiLine = new StringBuilder();
foreach (DataGridViewRow r in dgvSm.Rows)
{
 if (!r.IsNewRow)
 {
  if (r.Cells.Count > 0)
  {
   multiLine.Append(r.Cells[0].Value.ToString()); //first separated
   for (int i = 1; i < r.Cells.Count; ++i)
   {
    singleLine.Append(','); //between values
    singleLine.Append(r.Cells[i].Value.ToString());
   }
   multiLine.AppendLine();
  }
 }
}

为了说明StringBuilder连接（只是动态字符数组）和字符串（每次使用operator + concatenation时新对象和复制所有内容）之间的速度差异，请查看迷你程序：

public static void Main()
{
    var sw = new Stopwatch();
    sw.Start();
    StringBuilder s = new StringBuilder();
    //string s = "";
    int i;
    for (i = 0; sw.ElapsedMilliseconds < 1000; ++i)
        //s += i.ToString();
        s.Append(i.ToString());
    sw.Stop();
    Console.WriteLine("using version with type " + s.GetType().Name + " I did " +
        i + " times of string concatenation.");
}

我的电脑是：

using version with type String I did 17682 times of string concatenation.
using version with type StringBuilder I did 366367 times of string concatenation.

Answer 2

试试这个：

    string multiLine = "";
string singleLine;    
foreach (DataGridViewRow r in dgvSm.Rows)
{
if (!r.IsNewRow)
{
singleLine = r.Cells[0].Value.ToString() + ","
+ r.Cells[1].Value.ToString() + ","
+ r.Cells[2].Value.ToString() + ","
+ r.Cells[3].Value.ToString() + "\r\n";
multiLine = multiLine + singleLine;
}
}

从DataGridView到多行逗号分隔的字符串

2 个答案: