Question

public class users
{
    public string id { get; set; }
    public string username { get; set; }
    public string password { get; set; }
    public string email { get; set; }
    public string country { get; set; }
}

public class IDaccesscontrol
{
    public static List<users> GetAllEmployees()
    {
        List<users> listEmployees = new List<users>();

        string CS = ConfigurationManager.ConnectionStrings["User_KarlConnectionString"].ConnectionString;
        using (SqlConnection con = new SqlConnection(CS))
        {
            SqlCommand cmd = new SqlCommand("Select from user_karl", con);
            con.Open();
            SqlDataReader rdr = cmd.ExecuteReader();
            while (rdr.Read())
            {
                users users = new users();
                users.id = rdr["id"].ToString();
                users.username = rdr["username"].ToString();
                users.password = rdr["password"].ToString();
                users.email = rdr["email"].ToString();
                users.country = rdr["country"].ToString();

                listEmployees.Add(users);
                con.Close();
            }
        }

        return listEmployees;
    }
}

}

Answer 1

尝试select * from user_karl。

您只是在SQL语句本身中出现语法错误。 C＃无法在编译时选择它，因此您将获得运行时异常。

如果您无法找到这些语法错误，有时它可以帮助将SQL语句复制/粘贴到SQL Server Management Studio并看到它告诉您那里。要获取应用程序发送到服务器的确切语句，请使用SQL事件探查器（SQL Server Management Studio中的“工具”菜单）。

Answer 2

正确的语法是从user_karl 中选择*。在上面的代码中，您错过了星号。它检索表格中的整个数据“user_karl”

在代码中更改此行：

SqlCommand cmd = new SqlCommand("Select * from user_karl", con);

Answer 3

Your code have some errors, not only sql-query. Change your code to the following:

public class users
{
public string id { get; set; }
public string username { get; set; }
public string password { get; set; }
public string email { get; set; }
public string country { get; set; }
}

public class IDaccesscontrol
{
public static List<users> GetAllEmployees()
{
    List<users> listEmployees = new List<users>();

    string CS = ConfigurationManager.ConnectionStrings["User_KarlConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(CS))
    {
        SqlCommand cmd = new SqlCommand("Select * from user_karl", con); //when selecting something from a database, you have to appoint exactly what you want to eject
//otherwise if will occur an error as you had. * means we want to eject all columns from the table
        con.Open();
        SqlDataReader rdr = cmd.ExecuteReader();
        while (rdr.Read())
        {
            users users = new users();
            users.id = rdr["id"].ToString();
            users.username = rdr["username"].ToString();
            users.password = rdr["password"].ToString();
            users.email = rdr["email"].ToString();
            users.country = rdr["country"].ToString();

            listEmployees.Add(users);
            //con.Close(); you are in the while loop, so you can't close connection until you will not finish your work with data
        }
            con.Close(); //working with your reader has been finished, so we can close connection
    }

    return listEmployees;
}

}

异常详细信息：System.Data.SqlClient.SqlException：关键字＆＃39; from＆＃39;附近的语法不正确

3 个答案: