[英]OleDB only returning DbNull, what have I done wrong?
我有以下代碼:
// personCount = 7291; correct value
int personCount = (int)new OleDbCommand("SELECT COUNT(*) AS [count] FROM [Individual]", _access).ExecuteScalar();
List<Person> people = new List<Person>();
OleDbCommand personQuery = new OleDbCommand("SELECT * FROM [Individual]", _access);
using (OleDbDataReader personReader = personQuery.ExecuteReader())
{
int curPerson;
while (personReader.Read())
{
curPerson++;
// This runs several times
if (personReader.IsDBNull(0)) continue;
// [snip] create a new Person and add it to people
}
// at this point, curPerson == 7291 but the list is empty.
}
這是我的確切代碼。 字段0是主鍵,因此永遠不應為null,但從數據庫返回的每一行都將所有字段設置為DBNull! 我看不出自己做錯了什么,有人可以對此有所了解嗎?
我的連接字符串是:
Provider = Microsoft.Jet.OLEDB.4.0; Data Source = C:\\ path \\ to \\ database.mdb
出於這樣或那樣的原因,使用*
列選擇器是混亂的列。 使用特定列表可以解決此問題。 我仍然很好奇為什么會發生這種情況。
固定版本:
OleDbCommand personQuery = new OleDbCommand("SELECT [ID], [Surname], ... FROM [Individual]", _access);
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