Sql连接错误从数据集ds开始，因为无法将数据输入表单：
using (SqlConnection con = new SqlConnection("Data Source=c:\\RegistrationMDB.accdb"))
{
SqlDataAdapter da = new SqlDataAdapter();
DataSet ds = new DataSet();
SqlCommand cmd = new SqlCommand("SELECT ID, PASSWORD FROM Students WHERE ID = @ID OR PASSWORD = @PASSWORD", con);
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add("@ID", SqlDbType.VarChar).Value = id;
cmd.Parameters.Add("@PASSWORD", SqlDbType.VarChar).Value = pw;
da.SelectCommand = cmd;
da.Fill(ds);
foreach (DataRow dr in ds.Tables[0].Rows)
{
iD = (dr["@ID"].ToString());
password = dr["@PASSWORD"].ToString();
}
if (iD == id && password == pw)
{
return true;
}
else
{
LogNotification = "ID/Password is incorrect";
return false;
}
}
我在获取登录工作时遇到sql错误，如何让ds工作以允许我连接到数据库并登录？ 该错误表示ds不正确，并且未捕获sql server异常
学生：
class Student : Person
{
private String iD;
private String password;
private String eMail;
private double gpa;
private String message;
public Student() : base()
{
this.iD = "";
this.password = "";
this.eMail = "";
this.gpa = 0;
}
public Student(String i, String pa, String eM, int gp) : base()
{
this.iD = i;
this.password = pa;
this.eMail = eM;
this.gpa = gp;
InsertDB();
}
public Student(String iD)
{
SelectDB(iD);
}
//++++++++++++++++ DATABASE Data Elements +++++++++++++++++
public System.Data.OleDb.OleDbDataAdapter OleDbDataAdapter;
public System.Data.OleDb.OleDbCommand OleDbSelectCommand;
public System.Data.OleDb.OleDbCommand OleDbInsertCommand;
public System.Data.OleDb.OleDbCommand OleDbUpdateCommand;
public System.Data.OleDb.OleDbCommand OleDbDeleteCommand;
public System.Data.OleDb.OleDbConnection OleDbConnection;
public string cmd;
public void DBSetup(){
// +++++++++++++++++++++++++++ DBSetup function +++++++++++++++++++++++++++
// This DBSetup() method instantiates all the DB objects needed to access a DB,
// including OleDbDataAdapter, which contains 4 other objects(OlsDbSelectCommand,
// oleDbInsertCommand, oleDbUpdateCommand, oleDbDeleteCommand.) And each
// Command object contains a Connection object and an SQL string object.
OleDbDataAdapter = new System.Data.OleDb.OleDbDataAdapter();
OleDbSelectCommand = new System.Data.OleDb.OleDbCommand();
OleDbInsertCommand = new System.Data.OleDb.OleDbCommand();
OleDbUpdateCommand = new System.Data.OleDb.OleDbCommand();
OleDbDeleteCommand = new System.Data.OleDb.OleDbCommand();
OleDbConnection = new System.Data.OleDb.OleDbConnection();
OleDbDataAdapter.DeleteCommand = OleDbDeleteCommand;
OleDbDataAdapter.InsertCommand = OleDbInsertCommand;
OleDbDataAdapter.SelectCommand = OleDbSelectCommand;
OleDbDataAdapter.UpdateCommand = OleDbUpdateCommand;
OleDbConnection.ConnectionString = "Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Reg"+
"istry Path=;Jet OLEDB:Database L" +
"ocking Mode=1;Data Source=c:\\RegistrationMDB.accdb;J" +
"et OLEDB:Engine Type=5;Provider=Microsoft.Jet.OLEDB.4.0;Jet OLEDB:System datab" +
"ase=;Jet OLEDB:SFP=False;persist security info=False;Extended Properties=;Mode=S" +
"hare Deny None;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Create System Database=False;Jet " +
"OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repai" +
"r=False;User ID=Admin;Jet OLEDB:Global Bulk Transactions=1";
}
public void SelectDB(String id)
{ //++++++++++++++++++++++++++ SELECT +++++++++++++++++++++++++
DBSetup();
cmd = "Select * from Students where ID = " + iD;
OleDbDataAdapter.SelectCommand.CommandText = cmd;
OleDbDataAdapter.SelectCommand.Connection = OleDbConnection;
Console.WriteLine(cmd);
try {
OleDbConnection.Open();
System.Data.OleDb.OleDbDataReader dr;
dr = OleDbDataAdapter.SelectCommand.ExecuteReader();
dr.Read();
id=iD;
setPassword(dr.GetValue(1)+"");
setEMail(dr.GetValue(2)+"");
setGpa(Double.Parse(dr.GetValue(3)+""));
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
finally
{
OleDbConnection.Close();
}
}
public void InsertDB() {
// +++++++++++++++++++++++++++ INSERT +++++++++++++++++++++++++++++++
DBSetup();
cmd = "INSERT into Students values(" + getID() + "," +
"'" + getPassword() + "'," +
"'" + getEMail() + "'," +
"'" + getGpa() + ")";
OleDbDataAdapter.InsertCommand.CommandText = cmd;
OleDbDataAdapter.InsertCommand.Connection = OleDbConnection;
Console.WriteLine(cmd);
try
{
OleDbConnection.Open();
int n = OleDbDataAdapter.InsertCommand.ExecuteNonQuery();
if (n==1)
Console.WriteLine("Data Inserted");
else
Console.WriteLine("ERROR: Inserting Data");
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
finally
{
OleDbConnection.Close();
}
}
public void updateDB()
{
//++++++++++++++++++++++++++ UPDATE +++++++++++++++++++++++++
cmd = "Update Students set ID = '" + getID() + "'," +
"Password = '" + getPassword() + "', " +
"Email = '" + getEMail() + "', " +
"GPA = " + getGpa();
OleDbDataAdapter.UpdateCommand.CommandText = cmd;
OleDbDataAdapter.UpdateCommand.Connection = OleDbConnection;
Console.WriteLine(cmd);
try
{
OleDbConnection.Open();
int n = OleDbDataAdapter.UpdateCommand.ExecuteNonQuery();
if (n==1)
Console.WriteLine("Data Updated");
else
Console.WriteLine("ERROR: Updating Data");
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
finally
{
OleDbConnection.Close();
}
}
public void deleteDB()
{
//++++++++++++++++++++++++++ DELETE +++++++++++++++++++++++++
cmd = "Delete from Students where ID = " + getID();
OleDbDataAdapter.DeleteCommand.CommandText = cmd;
OleDbDataAdapter.DeleteCommand.Connection = OleDbConnection;
Console.WriteLine(cmd);
try
{
OleDbConnection.Open();
int n = OleDbDataAdapter.DeleteCommand.ExecuteNonQuery();
if (n==1)
Console.WriteLine("Data Deleted");
else
Console.WriteLine("ERROR: Deleting Data");
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
finally
{
OleDbConnection.Close();
}
}
public void setID(String iD)
{
this.iD = iD;
}
public void setPassword(String password)
{
this.password = password;
}
public void setEMail(String eMail)
{
this.eMail = eMail;
}
public void setGpa(double gpa)
{
this.gpa = gpa;
}
public String getID()
{
return iD;
}
public String getPassword()
{
return password;
}
public String getEMail()
{
return eMail;
}
public double getGpa()
{
return gpa;
}
public String getMessage()
{
return this.message;
}
public string LogNotification { get; set; }
public bool ConfirmLogin(string id, string pw)
{
using (SqlConnection con = new SqlConnection("Data Source=c:\\RegistrationMDB.accdb"))
{
SqlDataAdapter da = new SqlDataAdapter();
DataSet ds = new DataSet();
SqlCommand cmd = new SqlCommand("SELECT ID, PASSWORD FROM Students WHERE ID = @ID OR PASSWORD = @PASSWORD", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("@ID", SqlDbType.VarChar).Value = id;
cmd.Parameters.Add("@PASSWORD", SqlDbType.VarChar).Value = pw;
da.SelectCommand = cmd;
da.Fill(ds);
foreach (DataRow dr in ds.Tables[0].Rows)
{
iD = (dr["@ID"].ToString());
password = dr["@PASSWORD"].ToString();
}
if (iD == id && password == pw)
{
return true;
}
else
{
LogNotification = "ID/Password is incorrect";
return false;
}
}
}
public void displays(){
System.Console.WriteLine("ID = "+ getID());
System.Console.WriteLine("Password = "+ getPassword());
System.Console.WriteLine("Email = " + getEMail());
System.Console.WriteLine("GPA = " + getGpa());
}
}
StudentLogin表格：
namespace Students
{
public partial class StudentLogin : Form
{
public StudentLogin()
{
InitializeComponent();
}
private void Logingo_Click(object sender, EventArgs e)
{
Student st = new Student();
if(st.ConfirmLogin(textBox1.Text,textBox2.Text)==false){
MessageBox.Show(st.LogNotification);
}
else{}
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
}
}
}
答案 0 :(得分：0)
它不会从try catch中捕获SQLException。要打印异常，请在catch中使用SQLException。
答案 1 :(得分：0)
错误：
当您的应用程序无法与数据库通信时，将显示发生与网络相关或特定于实例的错误 建立与SQL Server的连接。找不到服务器或 无法访问。验证实例名称是否正确 SQL Server配置为允许远程连接。
。你应该看看它可能是你的ConnectionString。