This is the MySQL table.
+-------+-------+ | p_int | p_uni | +-------+-------+ | 0 | seat | | 1 | X400 | | 4 | X400 | | 2 | X400 | | 2 | X4SVR | | 3 | X400 | +-------+-------+ 6 rows in set
In the MasterPage of website developed an ASP.NET with Visual Studio 2019, C# and .NET Framework 4.7, I have create two List<string> using the values of MySQL table, as
List<string> Listp_uni = new List<string>();
List<string> Listp_int = new List<string>();
Container.p_int = reader["p_int"].ToString();
Container.p_uni = reader["p_uni"].ToString();
Listp_uni.Add(Container.p_uni.ToString());
Listp_int.Add(Container.p_int.ToString());
Container.p_uni = string.Join(",", Listp_uni.Select(e => "'" + e + "'").Distinct());
Container.p_int = string.Join(" ", Listp_int.Select(e => "" + e + "").Distinct());
the return’s of these List<string> are
'seat','X400','X4SVR' 0 1 4 2 3
I need select from the List<string> Listp_uni the value equal to X4SVR using LINQ
I have try without success
var studentNames = Mp.Container.p_uni.Where(s => s.Mp.Container.p_uni == "X4SVR")
.Select(s => s);
the error is
Compiler Error Message: CS1061: ‘char’ does not contain a definition
for ‘Mp’ and no extension method ‘Mp’ accepting a first argument of
type ‘char’ could be found (are you missing a using directive or an
assembly reference?)
How can I do it?
Editing question
public static class Container
{
public static string p_int
{
get
{
if (HttpContext.Current.Session["p_int"] != null)
{
return HttpContext.Current.Session["p_int"].ToString();
}
return null;
}
set
{
HttpContext.Current.Session["p_int"] = value;
}
}
public static string p_uni
{
get
{
if (HttpContext.Current.Session["p_uni"] != null)
{
return HttpContext.Current.Session["p_uni"].ToString();
}
return null;
}
set
{
HttpContext.Current.Session["p_uni"] = value;
}
}
}
string constr = ConfigurationManager.ConnectionStrings["cn"].ConnectionString;
using (MySqlConnection con =
new MySqlConnection(constr))
{
using (MySqlCommand cmd =
new MySqlCommand())
{
try
{
if (username != null)
{
con.Open();
cmd.Connection = con;
cmd.CommandText = "SP_ML_AUTE";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("tusername", username.ToString().ToUpper());
using (MySqlDataReader reader =
cmd.ExecuteReader())
{
if (reader.HasRows)
{
while (reader.Read())
{
Container.p_int = reader["p_int"].ToString();
Container.p_uni = reader["p_uni"].ToString();
Listp_uni.Add(Container.p_uni.ToString());
Listp_int.Add(Container.p_int.ToString());
}
Container.p_uni = string.Join(",", Listp_uni.Select(e => "'" + e + "'").Distinct());
Container.p_int = string.Join(" ", Listp_int.Select(e => "" + e + "").Distinct());
}
}
}
}
catch (Exception ex)
{
throw new ApplicationException("operation failed!", ex);
}
finally
{
cmd.Connection.Close();
}
}
}
new editing
DataTable dt = new DataTable();
dt.Columns.Add("p_int", typeof(int));
dt.Columns.Add("p_uni", typeof(string));
dt.Rows.Add(new object[] { 0, "seat" });
dt.Rows.Add(new object[] { 1, "X400" });
dt.Rows.Add(new object[] { 4, "X400" });
dt.Rows.Add(new object[] { 2, "X400" });
dt.Rows.Add(new object[] { 2, "X4SVR" });
dt.Rows.Add(new object[] { 3, "X400" });
string p_int = string.Join(",", dt.AsEnumerable().Select(x => x.Field<int>("p_int")).Distinct());
string p_uni = string.Join(" ", dt.AsEnumerable().Select(z => z.Field<string>("p_uni")).Distinct());
Response.Write(p_int + "<br />" + p_uni + "<br /><br />");
var studentNames = p_uni.Where(s => s.p_uni == "X4SVR").Select(s => s);
Response.Write(studentNames);
Answers:
Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.
Method 1
Firstly you have to understand we cannot use select in string.
The main functions are in the link please go through it String functions .
In the below code I’ve created some examples for selecting
“X4SVR” . Please check. My code is not a better one .But it will give you some insight to solve your issue.
Happy coding 🙂
DataTable dt = new DataTable();
dt.Columns.Add("p_int", typeof(int));
dt.Columns.Add("p_uni", typeof(string));
dt.Rows.Add(new object[] { 0, "seat" });
dt.Rows.Add(new object[] { 1, "X400" });
dt.Rows.Add(new object[] { 4, "X400" });
dt.Rows.Add(new object[] { 2, "X400" });
dt.Rows.Add(new object[] { 2, "X4SVR" });
dt.Rows.Add(new object[] { 3, "X400" });
string p_int = string.Join(",", dt.AsEnumerable().Select(x => x.Field<int>("p_int")).Distinct());
string p_uni = string.Join(" ", dt.AsEnumerable().Select(z => z.Field<string>("p_uni")).Distinct());
Response.Write(p_int + "<br />" + p_uni + "<br /><br />");
// if you want to get p_uni and p_int take from the datatable itself
//it will return matching p_uni and p_int
var studentNames = dt.AsEnumerable().Where(s => s.Field<string>("p_uni") == "X4SVR").Select(y => y);
//if you want get the name only
//Method - using the array
string [] p_uniArray = dt.AsEnumerable().Select(z => z.Field<string>("p_uni")).ToArray();
var studentNames1 = p_uniArray.AsEnumerable().Where(s => s == "X4SVR").Select(y => y);
//if you need to take from p_uni string it self please convert it into array like
//here you are not using any separator so I'm splitting it with space
var stName = p_uni.Split(" ");
var studentNames2 = stName.Where(x => x == "X4SVR").Select( y => y).Distinct();
// var studentNames = dt.Where(s => s.p_uni == "X4SVR").Select(s => s);
Response.Write(studentNames);
Method 2
Try following from a datatable :
DataTable dt = new DataTable();
dt.Columns.Add("p_int", typeof(int));
dt.Columns.Add("p_uni", typeof(string));
dt.Rows.Add(new object[] { 0, "seat"});
dt.Rows.Add(new object[] { 1, "X400"});
dt.Rows.Add(new object[] { 4, "X400"});
dt.Rows.Add(new object[] { 2, "X400"});
dt.Rows.Add(new object[] { 2, "X4SVR"});
dt.Rows.Add(new object[] { 3, "X400"});
string p_int = string.Join(",", dt.AsEnumerable().Select(e => e.Field<int>("p_int")).Distinct());
string p_uni = string.Join(" ", dt.AsEnumerable().Select(e => e.Field<string>("p_uni")).Distinct());
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0