Question

对于我已经构建的应用程序，我已经使用了followig函数来允许表导出到csv：

`protected void Export_Click(object sender, EventArgs e)
{
    DataTable dt = (DataTable)Session["datatable"];
    String names = (String)Session["names"];
    DataRow total = dt.Rows[dt.Rows.Count - 1]; 
    List<string> colSaved = new List<string>();

    for (int n = dt.Columns.Count -1 ; n >= 0; n--)
    {
        if (total[n].ToString() != "0")
        { 
            colSaved.Add(dt.Columns[n].ColumnName);

        }
    }

    string[] columns = colSaved.ToArray();
    DataTable newTable;
    newTable = dt.DefaultView.ToTable( false, columns);
    String[] content = new String[newTable.Rows.Count + 1];

    string temp1 = "";
    content[0] = names;

    for (int i =0; i<newTable.Rows.Count;i++)

{ temp1 =“”;

    for (int j = 0; j < newTable.Columns.Count; j++)
{

    temp1 += "\"" + newTable.Rows[i][j] + "\",";
    content[i + 1] = temp1;
}

}

    string name = DateTime.Now.Year + "" + DateTime.Now.Month + "" + DateTime.Now.Day +      "" + DateTime.Now.Hour + "" + DateTime.Now.Minute + "" + DateTime.Now.Second + "" +  DateTime.Now.Millisecond + "__" + ".csv";
   System.IO.File.WriteAllLines(Server.MapPath("~/export/" + name), content);

Response.Redirect（“〜/ export /”+ name）;

}`

其中dt是一个旋转数据表。问题是在应用程序中我删除了值为“0”的列，但在导出的文件中，它们确实出现了。我还需要一个函数来从导出的表中删除这些列。有人可以帮助我吗？

Answer 1

假设您有一个包含A，B，C，D列的DataTable，现在您希望DataTable的另一个实例具有相同的行但仅包含A，B，D列（已根据您的要求删除了C ）

DataTable dt = GetTable(); //This is the table with A, B, C and D columns....

string[] columns = new string[] {"A", "B", "D"};
DataTable newTable;   // This will have only A, B, and D
newTable = dt.DefaultView.ToTable("tempTableName", false, columns);

您可以看到的问题是要知道要保留原始源的列的名称。

MSDN on DataView.ToTable methods

然后可以用这种方式重写准备字符串数组的循环

StringBuilder sb = new StringBuilder();
sb.AppendLine(Session["names"].ToString());

foreach(DataRow r in newTable.Rows)
{
    sb.AppendLine("\"" + string.Join("\",", r.ItemArray) + "\"");
}
string name = DateTime.Now.Year + "" + DateTime.Now.Month + "" + DateTime.Now.Day + "" + DateTime.Now.Hour + "" + DateTime.Now.Minute + "" + DateTime.Now.Second + "" + DateTime.Now.Millisecond + "__" + ".csv";
System.IO.File.WriteAllText(Server.MapPath("~/export/" + name), sb.ToString());
Response.Redirect("~/export/" + name);

编辑上述更新后，获取要保留在新表格中的列名称相对容易

List<string> colSaved = new List<string>();
for (int n = dt.Columns.Count - 1; n >= 0; n--)
{
    if (total[n].ToString() != "0")
        colSaved.Add(dt.Columns[n].ColumnName);
}
.....
.....
string[] columns = colSaved.ToArray();

这将使原始表（dt和Session变量）保留原始列，而newTable将包含仅保存的列的行。

请注意，如果循环一个集合以从中删除一些元素，最好从集合的最后一个元素开始并循环到第一个元素，从集合的尾部删除元素（无需调整for indexer）

Answer 2

 protected void Export_Click(object sender, EventArgs e)
{


    DataTable dt = (DataTable)Session["datatable"];
    String names = (String)Session["names"];
    DataRow total = dt.Rows[dt.Rows.Count - 1]; //rreshti i fundit
    List<string> colSaved = new List<string>();

    for (int n = dt.Columns.Count-1; n >=0; n--)

    {

        if (total[n].ToString() != "0")  
            colSaved.Add(dt.Columns[n].ColumnName);


    }

string[] columns = colSaved.ToArray();

DataTable newTable;
newTable = dt.DefaultView.ToTable(false, columns);
StringBuilder sb = new StringBuilder();

sb.AppendLine(string.Join(",",columns.Reverse()));

foreach (DataRow r in newTable.Rows)
{

         sb.AppendLine(string.Join(",", r.ItemArray.Reverse()));
}
string name = DateTime.Now.Year + "" + DateTime.Now.Month + "" + DateTime.Now.Day + "" + DateTime.Now.Hour + "" + DateTime.Now.Minute + "" + DateTime.Now.Second + "" + DateTime.Now.Millisecond + "__" + ".csv";
System.IO.File.WriteAllText(Server.MapPath("~/export/" + name), sb.ToString());
Response.Redirect("~/export/" + name);

}

这是功能，它最终有效！

从导出的表中删除列

2 个答案: