.NET-使用DataSet从MS Access DB获取行

Question

I have a MS Access database I am trying to access in C# using a DataSet. However, while it can get the table's columns, it doesn't see any of its rows.

Here is the code:

    private void Button_Start_Click(object sender, EventArgs e)
    {
        StringBuilder S = new StringBuilder();

        DataTable TheTable = DataSet_TheData.TheTable;

        DataColumnCollection Cols = TheTable.Columns;

        DataTableReader Rows = TheTable.CreateDataReader();
        while (Rows.Read())
        {
            long Id = Rows.GetInt64(0);
            DateTime StartTime = Rows.GetDateTime(3);
            S.AppendLine(Id.ToString() + " - " + StartTime.ToString("M/d h:mm tt"));
        }
        S.AppendLine("Finished reading data");

        Text_Output.Text = S.ToString();
    }

DataSet_TheTable is a DataSet pointing to an Access database defined in design. Text_Output is a TextBox.

The table contains five rows.
However, Rows.Read always returns false. Also, if I try to access DataSet_TheData.TheTable.Rows before the loop, it shows zero rows. Cols is populated correctly from the Access table, so it's not a case of it not being able to find the table.

Replacing "TheTable.CreateDataReader()" with "new DataTableReader(TheTable)" does not work either.

How do I get the code to find the rows in the table?

Answer 1

To loop through the rows of a DataTable in c# you just need to do:

foreach (DataRow myRow in DataSet_TheData.Tables[0].Rows) {
    //Work with myRow here.
}

This will loop through the 5 rows in the DataTable returned to you.

Then, on each row you just access the value of a column for a specific row by using:

myRow["myColumnName"]

---

If you want to do this programatically for each row:

foreach (DataRow myRow in DataSet_TheData.Tables[0].Rows) {
    foreach (DataColumn myCol in DataSet_TheData.Tables[0].Columns) {
       //Use myRow[myCol] here
    }
}

Answer 2

It appears that Visual Studio doesn't so much as link to the existing Access Database as make an internal empty copy of its tables, which is why the columns showed up but the rows did not. When I added this code, the table data was populated:

TestAccessDatabaseDataSetTableAdapters.TheTableTableAdapter A =
     new TestAccessDatabaseDataSetTableAdapters.TheTableTableAdapter();
A.Fill(TheDataSet.TheTable);

Boy, that was intuitive...