我試圖通過單擊按鈕(btnsearch_Click)來訪問我主窗體中的事件,每次單擊它時,都會顯示'對象引用未設置爲對象的實例'。NullReferenceException未處理 - 什麼是空?
這裏是我的代碼:
用戶控件
namespace Purchase_Order
{
public partial class Search : UserControl
{
public event EventHandler btnSearchClicked;
public Search()
{
InitializeComponent();
}
private void btnsearch_Click(object sender, EventArgs e)
{
btnSearchClicked(sender, e);
}
}
}
主要形式
namespace Purchase_Order
{
public partial class formMain : Form
{
public formMain()
{
InitializeComponent();
}
private void formMain_Load(object sender, EventArgs e)
{
Search searchbox = new Search();
searchbox.btnSearchClicked += new EventHandler(SearchClicked);
}
void SearchClicked(object sender, EventArgs e)
{
MySqlConnection con = new MySqlConnection(serverstring);
try
{
string query = "SELECT * FROM tblclassification WHERE INSTR(class_name, @search)";
MySqlCommand cmd = new MySqlCommand(query, con);
MySqlDataAdapter da = new MySqlDataAdapter(cmd);
Search content = new Search();
cmd.Parameters.AddWithValue("@search", content.btnsearch.Text);
DataTable dt = new DataTable();
da.Fill(dt);
classification control = new classification();
control.dataGridView1.DataSource = dt;
control.dataGridView1.DataMember = dt.TableName;
panelMain.Controls.Clear();
panelMain.Controls.Add(control);
MessageBox.Show("OK");
}
catch (Exception)
{
throw;
}
finally
{
if (con.State == ConnectionState.Open)
{
con.Close();
}
}
}
凡'serverstring'初始化? – 2013-04-30 07:16:28
你可以看到在哪一行使用visual studio調試器拋出的錯誤 – 2013-04-30 07:19:48
@AntP對不起,我忘了複製服務器字符串代碼,這裏是: string serverstring =「user id = root; password =; server = localhost; database = purchase_order;連接超時= 3;「; – Harvey 2013-04-30 07:21:05