我正在尝试从我的页面中选择一个用户，并在我已经创建注册表单的页面default_information.aspx.cs上显示该用户信息。registration.aspx
我收到System.NullReferenceException:Object reference not set to an instance of an object错误。请帮我。我已经给出了它的主要部分。我调试了它。我发现每个数据都是从我的数据库中选择的string strusername , strpassword. usernametxt.Text = strusername;但是当我尝试在该文本字段上显示用户名或密码时，代码会中断。
default_information 包含
protected void gridviewprofile_SelectedIndexChanged(object sender, EventArgs e)
{
registration objdef = new registration();
string username = gridviewprofile.Rows[gridviewprofile.SelectedIndex].Cells[1].Text;
objdef.displayuser(username);
}
protected void update_Click(object sender, EventArgs e)
{
Response.Redirect("registration.aspx");
}
registration.aspx 包含
protected void register_Click(object sender, EventArgs e)
{
user objuser = new user();
objuser.username = usernametxt.Text;
objuser.password = passwordtxt.Text;
objuser.email = emailtxt.Text;
objuser.Save();
}
public void displayuser(string username)
{ user obj = new user();
DataSet objDataset = obj.profile(username);
string strusername = objDataset.Tables[0].Rows[0][0].ToString();
string strpassword = objDataset.Tables[0].Rows[0][1].ToString();
string stremail = objDataset.Tables[0].Rows[0][2].ToString();
usernametxt.Text = strusername;
passwordtxt.Text = strpassword;
emailtxt.Text = stremail;
}
用户类包含
public class user
{
public void Save()
{
clssqlserver obj = new clssqlserver();
obj.insertuser_info(Username,Password,Email);
}
public DataSet profile(string username)
{
clssqlserver obj = new clssqlserver();
return obj.getalluser_info(username);
}
}
clssqlserver 包含
public DataSet getalluser_info(string username)
{
string connectionstring = "Data Source=localhost\\mssql;Initial Catalog=blooddb;Integrated Security=True";
SqlConnection objconnection = new SqlConnection(connectionstring);
objconnection.Open();
string command = "Select * from login_donor where username='" + username + "' ";
SqlCommand objcommand = new SqlCommand(command, objconnection);
DataSet objdataset = new DataSet();
SqlDataAdapter objadapter = new SqlDataAdapter(objcommand);
objadapter.Fill(objdataset);
objconnection.Close();
return objdataset;
}
public bool insertuser_info(string username,string password,string email)
{ string connectionstring = "Data Source=localhost\\mssql;Initial Catalog=blooddb;Integrated Security=True";
SqlConnection objconnection = new SqlConnection(connectionstring);
objconnection.Open();
string strInsertCommand = "insert into login_donor values('"+ username +"','"+ password + "','"+email+"')";
SqlCommand objcommand = new SqlCommand(strInsertCommand, objconnection);
objcommand.ExecuteNonQuery();
objconnection.Close();
return true;
}