datatable常用函数

通过条件查询并排序得到新的DT

string clumname = "";
string filtcontext = "";
string wherecode = clumname + "='" + filtcontext + "'";

/// <summary>
/// 通过条件查询并排序得到新的DT
/// </summary>
/// <param name="dt">源DT</param>
/// <param name="wherecode">查询条件</param>
/// <param name="orderby">排序</param>
/// <returns>根据给定的DT生成新的DT</returns>
public static DataTable ScreeningDataTable(DataTable dt, string wherecode, string orderby)
{
    DataTable newdt = new DataTable();
    newdt = dt.Clone();
    DataRow[] dr = dt.Select(wherecode, orderby);
    for (int i = 0; i < dr.Length; i++)
    {
        newdt.ImportRow((DataRow)dr[i]);
    }
    return newdt;//返回的查询结果
}

通过条件查询得到新的DT

/// <summary>
/// 通过条件查询得到新的DT
/// </summary>
/// <param name="dt">源DT</param>
/// <param name="wherecode">查询条件</param>
/// <returns>根据给定的DT生成新的DT</returns>
public static DataTable ScreeningDataTable(DataTable dt, string wherecode)
{
    DataTable newdt = new DataTable();
    newdt = dt.Clone();
    DataRow[] dr = dt.Select(wherecode);
    for (int i = 0; i < dr.Length; i++)
    {
        newdt.ImportRow((DataRow)dr[i]);
    }
    return newdt;//返回的查询结果
}

统计DataTable中某一列不同值

DataTable dtyouliao = new DataTable();
//统计DataTable中某一列不同值 筛选车号不重复值
DataView dtview = dtyouliao.DefaultView;
DataTable dtTemporary = new DataTable();//车号dt
dtTemporary = dtview.ToTable(true, "车号");
dataGridView1.DataSource = dtTemporary;

打开文件夹并遍历所有.xls* 的内容

FolderBrowserDialog dialog = new FolderBrowserDialog();
dialog.ShowNewFolderButton = false;
dialog.Description = "请选择文件路径";
if (defaultfilePath != "")
{
    //设置此次默认目录为上一次选中目录  
    dialog.SelectedPath = defaultfilePath;
}
DialogResult result = dialog.ShowDialog();
if (result == DialogResult.OK || result == DialogResult.Yes)
{
    string foldPath = dialog.SelectedPath;
    defaultfilePath = foldPath;
    string[] files = Directory.GetFiles(defaultfilePath + @"\", "*.xls*");
    foreach (string file in files)
    {
        // MessageBox.Show(file);
        string currPath = file.Substring(0, file.LastIndexOf(@"\"));
        string excelname = file.Substring(file.LastIndexOf(@"\") + 1, file.LastIndexOf(@".xls") - file.LastIndexOf(@"\") - 1);
        DataTable dtinput = new DataTable();
        dtinput = NPOI_Excel.ExcelToDataTable(file, true, 3);
        dtinput.TableName = excelname;
        dtsdanxiangkaoke.Add(dtinput);
    }
}