在asp.net中连接的SQL Server数据库文件但查询未执行

Question

I connected a .MDF database file to my aspx file in C# (Visual Studio), but when I'm trying to execute a query it doesn't work.

Given below is the code where the problem occurs. Please help me out.

The com.ExecuteNonQuery() returns -1, I guess it should return 1 in case of a successful execution

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\karunya\Documents\Visual Studio 2010\Projects\Login\Login\App_Data\MyDB.mdf;Integrated Security=True;User Instance=True");

con.Open();
string sql = "SELECT * FROM Data WHERE user = '"+user.Text+"' ";
SqlCommand com = new SqlCommand(sql, con);
int tmp = Convert.ToInt32(com.ExecuteNonQuery());

con.Close();

if (tmp == 1)
{
    con.Open();
    sql = "SELECT pass FROM LogTable WHERE user = '" + user.Text + "'";
    SqlCommand com1 = new SqlCommand(sql, con);
    string password = com1.ExecuteScalar().ToString();

    if (password == pass.Text)
    {
       Response.Write("Access Granted!");
    }
    else
    {
       Response.Write("Access Denied!");
    }
 }
 else
 {
    Response.Write("User Name Incorrect!");
 }

Answer 1

what you trying to do ?

it will always return -1 because you are selecting tables

do this ..

 DataTable dt = new DataTable();
        using (var conn = new SqlConnection(connectionLib))
        {
            try
            {
                using (var cmd = new SqlCommand(Query, conn))
                {

                    SqlDataAdapter da = new SqlDataAdapter(cmd);
                    da.Fill(dt);
                    conn.Close();
                    da.Dispose();
                }
            }
            catch
            {
            }
        }

now check condition according to you if you want to check no of row then check

dt.rows.cout

Answer 2

Instead of relying on the return value of ExecuteNonQuery , use a COUNT(*) inside the query and return the count using ExecuteScalar .

And always (ALWAYS) use parameterized queries:

string sql = "SELECT COUNT(*) FROM Data WHERE user = @user";
SqlCommand com = new SqlCommand(sql, con);
com.Parameters.AddWithValue("@user", user.Text);
int tmp = Convert.ToInt32(com.ExecuteScalar());

And move the call to Close() towards the end of the method

Answer 3

please try to check if the connections string it's ok then try this code

you will know if the select hjas rows or not than do what you want to do

       con.Open();
                            cmd.Connection = con;
                            cmd.CommandText = "select * from user where login=@login and pass=@psw";
                            cmd.Parameters.Add(new SqlParameter("@login", SqlDbType.VarChar, 255)).Value = txtpsedu.Text;
                            cmd.Parameters.Add(new SqlParameter("@psw", SqlDbType.VarChar, 255)).Value = txtlogin.Text;

   dr = cmd.ExecuteReader();

                    if (dr.Read())
                    {

                   //// do  what  you  want  here  

                    }

                    else
                    {

                        Response.Write("User Name Incorrect!");

                    }
                    dr.Close();
                    con.Close();

i hope to try it