从适配器检索特定项目？

Question

I've got this block of code in C# code-behind that fills a combo box:

ddlRole.Items.Clear();
ddlRole.SelectedValue = null;
DataTable DDLRoles = new DataTable();
using (SqlConnection con2 = new SqlConnection(ConfigurationManager.ConnectionStrings["CLTDPL"].ConnectionString))
{
    //SqlDataAdapter adapter = new SqlDataAdapter("Select [Role_ID], [Role] from [MOS_Role] where [Function_ID] = " + FunID + " ORDER BY [Role] ASC", con2);
    SqlDataAdapter adapter = new SqlDataAdapter("Select [Role_ID], [Role], [BILLABLE_LBL] from [MOS_Role] where [Function_ID] = @FunID ORDER BY [Role] ASC", con2);
    adapter.SelectCommand.Parameters.AddWithValue("@FunID", Convert.ToInt32(ddlFunction.SelectedValue));
    adapter.Fill(DDLRoles);
    ddlRole.DataSource = DDLRoles;
    ddlRole.DataTextField = "Role";
    ddlRole.DataValueField = "Role_ID";
    ddlRole.DataBind();

}
ddlRole.Items.Insert(0, new ListItem("Select your role", "0"));

Now I'm being asked to change a label based on the field [BILLABLE_LBL]. So, I need to check if that field is NULL or 0, and write an If/Else statement based on that. However, I can't figure out how to get that value.

I mean, I could make a separate call to the data and use a reader, but that can't be the most efficient way.

Answer 1

I hope I understand the question correctly but you want to change a field according to the selected Role from the combo box and don't know how to get the [BILLABLE_LBL] value (feel free to correct me).

You can get the DataRow from your DataTable via the Select() method.

DataRow[] row = DDLRole.Select("Role_ID = '" + selectedValueFromCombobox + "'");

Now that you have your matching DataRow you can read out the desired value:

string labelText = (row[0]["BILLABLE_LBL"] != DBNull.Value && row[0]["BILLABLE_LBL"] != 0) ? (string)row[0]["BILLABLE_LBL"] : "Empty Field";

This call checks if the [BILLABLE_LBL] is Null or 0 like you wanted. If it is not Null or 0, it takes the value and saves it as string labelText . Else you can set an alternative text like "Empty Field" or just "";

I assume you have a Listener on your ComboBox to check when the value changes, or a "Commit Button" or some other method where you retrieve the selected Role value. Just add the code to your method/listener to get your desired value and set it as text for your label.

---

EDIT : Maybe this is more what you were looking for, since you don't need to use Select() on the datatable:

DataRowView selectedRow = (ddlRole.SelectedItem as DataRowView);

To retrieve values from the row you can just use: selectedRow["BILLABLE_LBL"] Now you can do your check for Null and 0 and you are good to go. I don't know which one is more efficient (Select or ... as DataRowView) but either way you get your value.

(Credit for the .SelectedItem as DataRowView to https://stackoverflow.com/a/9825085/5332988 )