DataTable行计数为空

本文关键字：DataTable | 更新日期: 2023-09-27 18:30:09

我正试图获取从OleDB查询中检索到的联系人列表，将其添加到列表中，然后将列表加载到DataTable中。当我计算列表中的项目数时，会得到正确的数字（27000）。

但是，当我计算DataTable中的行数时，结果是0。完成此操作后，我想使用FileHelpers将DataTable写入CSV，但是CSV文件是空的。

这是我正在使用的代码；

var listOfContacts = new List<Contact>();
using (OleDbConnection dbfCon = new OleDbConnection(dbfConstr))
{
    dbfCon.Open();
    var dbfCmd = new OleDbCommand(@"SELECT ct_id, ct_cmpid, ct_empid,
    ct_pplid, ct_cntid, ct_pplnm, ct_date, ct_time, ct_type, ct_doneby, ct_desc
    FROM contacts", dbfCon);
    using (var myReader = dbfCmd.ExecuteReader())
    {                       
        while (myReader.Read())
        {
            var newContact = new Contact()
            {
                ContactID = Convert.ToInt32(myReader[0]),
                CompanyID = Convert.ToInt32(myReader[1]),
                EmployeeID = Convert.ToInt32(myReader[2]),
                PersonID = Convert.ToInt32(myReader[3]),
                ContractID = Convert.ToInt32(myReader[4]),
                PersonName = myReader[5].ToString(),
                ContactDate = Convert.ToDateTime(myReader[6]),
                ContactTime = Convert.ToDateTime(myReader[7]),
                TypeOfContact = myReader[8].ToString(),
                ContactMadeBy = myReader[9].ToString(),
                ContactDescription = myReader[10].ToString(),                           
            };
            listOfContacts.Add(newContact);
        }
    }
    DataTable dTable = new DataTable();
    dTable.Columns.Add("ContactID");
    dTable.Columns.Add("CompanyID");
    dTable.Columns.Add("EmployeeID");
    dTable.Columns.Add("PersonID");
    dTable.Columns.Add("ContractID");
    dTable.Columns.Add("PersonName");
    dTable.Columns.Add("ContactDate");
    dTable.Columns.Add("ContactTime");
    dTable.Columns.Add("TypeOfContact");
    dTable.Columns.Add("ContactMadeBy");
    dTable.Columns.Add("ContactDescription");
    MessageBox.Show(listOfContacts.Count.ToString());
    foreach (var contact in listOfContacts)
    {
        var newRow = dTable.NewRow();
        newRow["ContactID"] = contact.ContactID;
        newRow["CompanyID"] = contact.CompanyID;
        newRow["EmployeeID"] = contact.EmployeeID;
        newRow["PersonID"] = contact.PersonID;
        newRow["ContractID"] = contact.ContractID;
        newRow["PersonName"] = contact.PersonName;
        newRow["ContactDate"] = contact.ContactDate;
        newRow["ContactTime"] = contact.ContactTime;
        newRow["TypeOfContact"] = contact.TypeOfContact;
        newRow["ContactMadeBy"] = contact.ContactMadeBy;
        newRow["ContactDescription"] = contact.ContactDescription;
    }
    MessageBox.Show(dTable.Rows.Count.ToString());

你可以看到导致数字的两个MessageBox，我是否错误地将数据加载到DataTable中？

DataTable行计数为空

您必须将新行添加到DataTable:

foreach (var contact in listOfContacts)
{
    var newRow = dTable.NewRow();
    newRow["ContactID"] = contact.ContactID;
    newRow["CompanyID"] = contact.CompanyID;
    newRow["EmployeeID"] = contact.EmployeeID;
    newRow["PersonID"] = contact.PersonID;
    newRow["ContractID"] = contact.ContractID;
    newRow["PersonName"] = contact.PersonName;
    newRow["ContactDate"] = contact.ContactDate;
    newRow["ContactTime"] = contact.ContactTime;
    newRow["TypeOfContact"] = contact.TypeOfContact;
    newRow["ContactMadeBy"] = contact.ContactMadeBy;
    newRow["ContactDescription"] = contact.ContactDescription;
    dTable.Rows.Add(newRow);  // YOU NEED THIS LINE TO ADD THE NEWROW TO DATATABLE
}

在foreach循环的末尾添加以下内容：

dTable.Rows.Add(newRow);
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