C#

Quote:

This is because the ValueTuple type's named elements are erased at runtime, meaning there's no runtime representation of them.

BillWoodruff wrote:

at run-time accessing that Property returns a result that has the field Names.

VTProp = ("hello", 23, "exit");

var vtp = VTProp;

string s2 = vtp.S2;     // uses the field Name ! 

var vtp = VTProp;
Console.WriteLine("S2: {0}", vtp.S2);

ldarg.0     
call        UserQuery.get_VTProp
stloc.0     // vtp
ldstr       "S2: {0}"
ldloc.0     // vtp
ldfld       System.ValueTuple<System.String,System.Int32,System.String>.Item3 // <-- NB: "Item3", not "S2".
call        System.Console.WriteLine

ValueTuple<string, int, string> vtp = VTProp;
Console.WriteLine("S2: {0}", vtp.Item3);

BillWoodruff wrote:

at run-time

Richard Deeming wrote:

Or perhaps I've misunderstood what you mean by the phrase "run-time"?

public (string S1, int I1, string S2) VTProp {set; get;} VTProp = ("hello", 23, "exit");

var vtp = VTProp;

string s2 = vtp.S2;     // uses the field Name ! 

Type t = VTProp.GetType();
Console.WriteLine(t.GetField("S2"));
// "null"


foreach (FieldInfo field in VTProp.GetType().GetFields())
{
    Console.WriteLine(field.Name);
}
// Item1
// Item2
// Item3


dynamic vtp = VTProp;
Console.WriteLine("S2: {0}", vtp.S2);
// RuntimeBinderException: 'System.ValueTuple<string,int,string>' does not contain a definition for 'S2'

Member 13685821 wrote:

i need coding for c# to make recovery software

How to get an answer to your question

Be specific!
Don't ask "can someone send me the code to create an application that does 'X'.
Pinpoint exactly what it is you need help with.

Member 13683765 wrote:

cmd.CommandText = "insert into tblBook (Book_ID, Name, Authour, Category, Donater_ID, Section_ID) values ('" + txtBoxBookId.Text + "', '" + txtBoxBookName.Text + "', '" + txtBoxAuthour.Text + "', '" + txtBoxCategory.Text + "', '" + txtBoxDonaterId.Text + "', '" + txtBoxSecId.Text + "')";

try
{
    string MyConnectionStringHere = "";
    using (var con = new SqlConnection(MyConnectionStringHere))
    using (var cmd = con.CreateCommand())
    {
        con.Open();
        cmd.CommandText = @"
        INSERT INTO tblBook (
            Book_ID,
            Name,
            Authour,
            Category,
            Donater_ID,
            Section_ID
            ) VALUES (
            @Book_ID,
            @Name,
            @Authour,
            @Category,
            @Donater_ID,
            @Section_ID)";
        cmd.Parameters.AddWithValue("@Book_ID", txtBoxBookId.Text);
        cmd.Parameters.AddWithValue("@Name", txtBoxBookName.Text);
        cmd.Parameters.AddWithValue("@Authour", txtBoxAuthour.Text);
        cmd.Parameters.AddWithValue("@Category", txtBoxCategory.Text);
        cmd.Parameters.AddWithValue("@Donater_ID", txtBoxDonaterId.Text);
        cmd.Parameters.AddWithValue("@Section_ID", txtBoxSecId.Text);
        if (1 == cmd.ExecuteNonQuery())
        {
            // declare success here!
        }
        else
        {
            // panic here.
        }
    }
}
catch (Exception ex)
{
    MessageBox.Show(ex.ToString());
}

• You'll still need to set a connection-string in the example, but you don't need SqlConnections in multiple methods, or as a member-variable. It will be closed when exiting the "using" statement.
  
• You want the complete exception-text; it will tell you where and more.
  
• Those column-names using up many lines may seem excessive to you; go stand on such a line in the IDE and press Ctrl-X. Move the cursor down two strokes and press Ctrl-V.
  

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]