如何从查询结果创建DropDownList？

Question

I have the following query:

protected void Filterbtn_Click(object sender, EventArgs e)
{
    string commandFilterUsers = "SELECT DISTINCT " + ddlFilterUsers.SelectedValue + " FROM UsersDB";
    string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open(); 
        SqlCommand sqlCommand = new SqlCommand(commandFilterUsers, connection);
        SqlDataAdapter adapter = new SqlDataAdapter(sqlCommand);
        adapter.Fill(dataset);
    }

I select a value from ddl1 and I need to create another one using the result of the query. What do I do?

Answer 1

Assuming the result of the query returns 2 column from the database: UserID,UserName The Column is indexed in the dataset table from left to right from index 0 to increasing order. Suppose your dropdownlist control ID="ddlShowResult" then use the following code:

      protected void Filterbtn_Click(object sender, EventArgs e)
            {
                string commandFilterUsers = "SELECT DISTINCT " + ddlFilterUsers.SelectedValue + " FROM UsersDB";
                string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                using (SqlConnection connection = new SqlConnection(connectionString))
                {
                    connection.Open();
                    SqlCommand sqlCommand = new SqlCommand(commandFilterUsers, connection);
                    SqlDataAdapter adapter = new SqlDataAdapter(sqlCommand);
                    adapter.Fill(dataset, "FillUser");
                }
                ddlShowResult.DataTextField = dataset.Tables["FillUser"].Columns[1].ToString();//User Name: Will be shown to user
                ddlShowResult.DataValueField = dataset.Tables["FillUser"].Columns[0].ToString();//User ID: will be used in backend
                ddlShowResult.DataSource = dt;
                ddlShowResult.DataBind();
            }