C＃遍历DataTable中的行

Question

I'm trying to Iterate through rows in a 2 column table to check 1 field in each row against a Name. Once found I want to code to assign the corresponding Number to the OurNumber variable, and break out of the loop by setting GotTheNumber to true.

Below is the code I'm using:

    private void BtnDelete_Click(object sender, EventArgs e)// Sends to ConfirmDeleteEMP Form 
    {            
        ConfirmDeleteEMP form = new ConfirmDeleteEMP();
        DataTable table = new DataTable();
        string connstring = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\HoliPlanData.accdb;Persist Security Info=False";
        using (OleDbConnection conn = new OleDbConnection(connstring))
        {
            string query = "SELECT PayrollNo, (FirstName + ' ' + LastName) AS NAME FROM [Employee]";                 
            OleDbDataAdapter adapter = new OleDbDataAdapter(query, conn);
            adapter.Fill(table);                                        
        }

        string SelectedName = DropBoxEmp.Text;            
        bool GotTheNumber = false;
        int OurNumber = 0;
        while (!GotTheNumber)
        {
            foreach (DataRow ThisRow in table.Rows)
            {
                if (SelectedName = (table.Rows[ThisRow])) 
                {
                    OurNumber = ///THATNUMBER///;
                    GotTheNumber = true;
                }  
            }
        }

        MessageBox.Show(SelectedName);
        var GoodNumber = (table.Rows[OurNumber]["PayrollNo"].ToString());
        form.PassValueName = SelectedName;
        form.PassSelectedPayroll = GoodNumber;               
        form.Tag = this;
        form.Show(this);
        Hide();
    }

I don't know where to go from the If statement, so any help would be greatly appreciated.

Answer 1

Looping through the rows in your client program is exactly what you don't want to do. Let the database do that work for you. Try this:

private void BtnDelete_Click(object sender, EventArgs e)// Sends to ConfirmDeleteEMP Form 
{     
    object result;       
    string query = "SELECT PayrollNo FROM [Employee] WHERE FirstName + ' ' + LastName = ?"; 
    string connstring = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\HoliPlanData.accdb;Persist Security Info=False";

    using (OleDbConnection conn = new OleDbConnection(connstring))
    using (OleDbCommand cmd = new OleDbCommand(query, conn))
    {
        //guessing at type and length here
        cmd.Parameters.Add("?", OleDbType.VarWChar, 50).Value = DropBoxEmp.Text;

        conn.Open();
        result = cmd.ExecuteScalar();                                        
    }

    if (result != null && result != DBNull.Value)
    {
        ConfirmDeleteEMP form = new ConfirmDeleteEMP();
        form.PassValueName = DropBoxEmp.Text;
        form.PassSelectedPayroll = (int)result;
        form.Tag = this;

        form.Show(this);
        Hide();
    }                    
}

If you really want to loop through the rows against all reason (it's slower, requires writing more code, and it's more error-prone), you can do this:

private void BtnDelete_Click(object sender, EventArgs e)// Sends to ConfirmDeleteEMP Form 
{                   
    DataTable table = new DataTable();
    string query = "SELECT PayrollNo, (FirstName + ' ' + LastName) AS NAME FROM [Employee]"; 
    string connstring = @"Provider = Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\HoliPlanData.accdb;Persist Security Info=False";
    using (OleDbConnection conn = new OleDbConnection(connstring))
    {                    
        OleDbDataAdapter adapter = new OleDbDataAdapter(query, conn);
        adapter.Fill(table);                                        
    }

    int PayrollNumber = 0;
    foreach (DataRow ThisRow in table.Rows)
    {
        if (DropBoxEmp.Text == ThisRow["NAME"])
        {
            PayrollNumber = (int)ThisRow["PayrollNo"];
            break;
        }  
    }
    //the whole loop could also be consolidated to this:
    //PayrollNumber = (int)table.Rows.First(r => r["NAME"] == DropBoxEmp.Text)["PayrollNo"];

    ConfirmDeleteEMP form = new ConfirmDeleteEMP();
    form.PassValueName = DropBoxEmp.Text;
    form.PassSelectedPayroll = PayrollNumber ;               
    form.Tag = this;
    form.Show(this);
    Hide();
}

Answer 2

Hm, hard to guess what exactly your problem is. But I think you just want to get the PayrollNo from the current row, aren't you?

Regarding the line further down ...

var GoodNumber = (table.Rows[OurNumber]["PayrollNo"].ToString());

... I think you could just call:

if (...)
{
    OurNumber = ThisRow["PayrollNo"].ToString();
    GotTheNumber = true;
}

However , I have no clue what you are doing with the following if-condition and if this really does what you want it to do:

if (SelectedName = (table.Rows[ThisRow]))
{
...
}