根据来自表单的用户输入，将一个表的主键插入另一个表

Question

I have a form with an asp:DropDownList that populates its contents from the Item_Description column in the Item table.

I would like to allow users to select an item from the drop-down list, and when the form is submitted, insert the ItemID value for the selected item into the Orders table using C#/T-SQL.

I could theoretically accomplish this with some lengthy if/else statements, but this seems too simple to require so much code.

I am able to update other tables by assigning asp:Textbox values to parameters and inserting them upon submission. I just can't seem to figure out how to pass the ItemID to the Orders table when a user selects a related item from the list.

PS I have already established a connection to my database, protected against SQL injection, etc.

Drop-down list:

ID="ddlItems"

Code for tables:

CREATE TABLE Item
(
    ItemID int primary key,
    Item_Description varchar(255)
); 

CREATE TABLE Orders
(
    OrderID int primary key,
    Order_Item varchar(255)
);

Code-behind method for Submit button click event:

protected void Submit_Click(object sender, EventArgs e)
{
    SqlConnection conn;
    SqlCommand comm;
    SqlDataReader reader;
    conn = new SqlConnection("Server=*omitted*");
    comm = new SqlCommand("INSERT INTO Orders VALUES @ItemID;", conn);

    comm.Parameters.Add("@ItemID", System.Data.SqlDbType.Int);
    comm.Parameters["@ItemID"].Value = <<<This is where I need help>>>;

    try
    {
        conn.Open();
        reader = comm.ExecuteReader();
        reader.Close();
    }
    catch
    {
        results.Text = "Error adding data. ";
    }
    finally
    {
        // Close the connection
        conn.Close();
        results.Text = "Added data.";
    }
}

Drop-down List binding:

<asp:DropDOwnList ID="ddlItems" runat="server" AutoPostBack="True" AppendDataBoundItems="True" DataSourceID="SqlDataSource1" DataTextField="Item_Description" DataValueField="Item_Description">
<asp:ListItem Value=""></asp:ListItem>
<asp:DropDownList>

Answer 1

As per you Quetion I think You Insert Query Does't Require Where Condition Just Remove the Condition

Bind DropDown Code

       DataSet ds = new DataSet();
        Cmd.CommandText = sqlcmd;
        Cmd.CommandTimeout = this.Timeout;
        Cmd.CommandType = CommandType.StoredProcedure;

        SqlDataAdapter sda = new SqlDataAdapter();
        sda.SelectCommand = Cmd;
        sda.Fill(ds);


        ddl.DataSource = ds.dt[0];
        ddl.DataTextField = ds.dt[0][COlumnname]
        ddl.DataValueField = ds.dt[0][ColumnName];
        ddl.DataBind();

Answer 2

I would join the Item and Orders table by ItemID, not Item_Description.

CREATE TABLE Item
(
    ItemID int primary key,
    Item_Description varchar(255)
); 

CREATE TABLE Orders
(
    OrderID int primary key,
    ItemID int 
);

I would set a referential constraint on ItemID.  ddlItems should have DataValueField of ItemID and DataTextField of Item_Description.

Assuming ItemID and OrderID are auto-incrementing, you could write:

SqlCommand comm = new SqlCommand("INSERT INTO Orders (ItemID) VALUES (@itemID)");

This is also assuming only one ItemID could be associated with an Order, otherwise, you would need Item, Order, and OrderItemAsc tables.

Answer 3

I am assuming that you are binding your drop downlist with the Item table.

So follow this approach.

1. Query would be (For binding drop downlist data from item table)

   select * from item

2. In C#

   ddlItems.DataSource = "your data table in which you are taking result of above query"; ddlItems.DataBind();

(I think you already have done the above steps)

3. Now just add two attribute to your drop down list in source like this.

    <asp:DropDownList ID="ddlItems" runat="server" DataTextField="Item_Description" DataValueField="ItemID " > 

4. Now you can directly access the id for selected item in drop down from c# code

   comm.Parameters["@ItemID"].Value= ddlItems.SelectedItem.Value;

Edit

Now looking at your edited question you just need to change DataValueField="ItemID" only :)