[英]Database Connection and Populating ListBox in Visual Basic
我想使用Visual Basic在Windows應用程序窗體中顯示結果,但我不斷收到此Exception錯誤:
System.Data.SqlClient.SqlException:'參數化查詢'(@Skill nvarchar(4000))SELECT a.Skill FROM拼寫INNER JOIN C'期望使用參數'@Skill',但未提供。
我不知道該怎么辦,謝謝您的時間和考慮
這是我的整個代碼:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Configuration;
using System.Data.SqlClient;
namespace rpg_game
{
public partial class Form1 : Form
{
SqlConnection connection;
string connectionString;
public Form1()
{
InitializeComponent();
connectionString=ConfigurationManager.
ConnectionStrings["rpg_game.Properties.Settings
.charactersConnectionString"].ConnectionString;
Populatebox();
}
private void Populatebox()
{
using (connection = new SqlConnection(connectionString))
using (SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM unit_tb", connection))
{
DataTable unit_table = new DataTable();
adapter.Fill(unit_table);
Name_list.DisplayMember = "Name";
Name_list.ValueMember = "Id";
Name_list.DataSource = unit_table;
}
}
private void Populatebox2()
{
string query = "SELECT a.Skill FROM Spells a INNER JOIN Character_Skills b ON a.Id = b.spell_id WHERE b.unit_id = @Skill";
using (connection = new SqlConnection(connectionString))
using (SqlCommand command = new SqlCommand(query,connection))
using (SqlDataAdapter adapter = new SqlDataAdapter(command))
{
command.Parameters.AddWithValue("@Skill", Class_list.SelectedValue);
DataTable unit_table2 = new DataTable();
adapter.Fill(unit_table2);
Class_list.DisplayMember = "Skill";
Class_list.ValueMember = "Id";
Class_list.DataSource = unit_table2;
}
}
private void Class_list_SelectedIndexChanged(object sender, EventArgs e)
{
Populatebox2();
}
}
}
需要參數“ @Skill”(未提供)。
消息清晰,查詢正常,但參數@Skill的值為null
因此請檢查Class_list.SelectedValue
我終於走了! 謝謝你的幫助!
意識到這一點后,我真的很傻,只需要更改代碼的這一部分即可:
command.Parameters.AddWithValue("@Skill",
Class_list.SelectedValue);
變成:
command.Parameters.AddWithValue("@Skill",
Name_list.SelectedValue);
由於我要執行的操作是獲取數據庫字符名稱的值,即“ JAY”,其值為1,然后將其復制到@skill中,作為一個結果:
每當我單擊一個新名稱時,他們的技能就會按照數據庫中的說明顯示
再次感謝大家的注意
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