遍历数据表以从每一行获取两个特定值 [英] looping through data table to get two specifics values from each row

问题描述

我正试图遍历数据表并打印出

• 的值0，


• 1和


• 每行第4个单元格，

感觉这应该可行，但我可能以某种方式弄乱了循环。

And it feels like this should be working but I'm probably messing up the loop somehow.

 foreach (DataRow dr in dt.Rows)
 {
      for (int x = 0; x < dt.Rows.Count; x++)
      {
          Console.WriteLine(dt.Columns[0].ColumnName + " ");
          Console.WriteLine(dt.Rows[x].ItemArray[0].ToString() + " ");
          Console.WriteLine(dt.Columns[1].ColumnName + " ");
          Console.WriteLine(dt.Rows[x].ItemArray[1].ToString() + " ");
          Console.WriteLine(dt.Columns[4].ColumnName + " ");
          Console.WriteLine(dt.Rows[x].ItemArray[4].ToString() + " ");
       }
 }

上面的代码给我这个错误：

The above code gives me this error:

系统无法执行指定的程序。

The system cannot execute the specified program.

推荐答案

您不需要在行上用 foreach 循环将 for 循环包围起来。 （您根本没有使用 dr ）

You don't need to surround your for loop with a foreach loop on the Rows. (You are not using the dr at all)

for (int idx = 0; idx < dt.Rows.Count; idx++)
{
    Console.WriteLine(dt.Columns[0].ColumnName + " ");
    Console.WriteLine(dt.Rows[idx].ItemArray[0] + " ");
    Console.WriteLine(dt.Columns[1].ColumnName + " ");
    Console.WriteLine(dt.Rows[idx].ItemArray[1] + " ");
    Console.WriteLine(dt.Columns[4].ColumnName + " ");
    Console.WriteLine(dt.Rows[idx].ItemArray[4] + " ");
}

更通用的版本：

int[] columnIndexes = new[] { 0, 1, 4 };
for (int rowIndex = 0; rowIndex < dt.Rows.Count; rowIndex++)
{
    for (int columnIndex = 0; columnIndex < columnIndexes.Length; columnIndex++)
    {
        Console.WriteLine(dt.Columns[columnIndex].ColumnName + " ");
        Console.WriteLine(dt.Rows[rowIndex].ItemArray[columnIndex] + " ");
    }
}

---

如果要遍历这样，您可以使用foreach进行行集合，但要复杂一些。

---

If you want to iterate through the Rows collection with foreach then you can do but it is a bit more trickier.

DataTable的Rows属性是 DataRowCollection 。它公开了 GetEnumerator 方法，这对于 foreach 循环必不可少。

DataTable's Rows property is a DataRowCollection. It exposes a GetEnumerator method, which is essential for the foreach loop.

foreach (DataRow dr in dt.Rows)
{
    //dr does not provide you direct access to the ColumnName
}

您不能直接从DataRow访问ColumnName。所有需要做的就是创建一个查找表。

You can't access the ColumnName from the DataRow directly. All need to do is to create a "lookup table" for the column names where the key is the index and the value is the name of the column.

int colIdx = 0;
var columnNames = dt.Columns
    .Cast<DataColumn>()
    .ToDictionary(_ => colIdx++, column => column.ColumnName);

之后，您的foreach循环将如下所示：

After that your foreach loop would look like this:

int[] columnIndexes = new[] {0, 1, 4};
foreach (DataRow row in dt.Rows)
{
    for (int columnIndex = 0; columnIndex < columnIndexes.Length; columnIndex++)
    {
        Console.WriteLine(columnNames[columnIndex] + " ");
        Console.WriteLine(row.ItemArray[columnIndex] + " ");
    }
}

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