C#

Rick_Bishop wrote:

public T ExecuteScalar<T>(string queryString, string connection_string)

private OleDbCommand CreateCommand(OleDbConnection connection, string queryString, object[] parameters)
{
    var command = new OleDbCommand("", connection);
    
    if (parameters != null && parameters.Length != 0)
    {
        // OleDb doesn't use named parameters, so convert them to positional:
        queryString = Regex.Replace(queryString, @"\{(\d+)\}", match =>
        {
            int index = int.Parse(match.Groups[1].Value);
            object value = parameters[index];
            string name = "@p" + command.Parameters.Count;
            command.Parameters.AddWithValue(name, value);
            return "?";
        });
    }
    
    command.CommandText = queryString;
    return command;
}

public T ExecuteScalar<T>(string queryString, params object[] parameters)
{
    using (OleDbConnection connection = new OleDbConnection(connection_string))
    using (OleDbCommand command = CreateCommand(connection, queryString, parameters))
    {
        var result = cmd.ExecuteScalar();
        if (Convert.IsDBNull(result)) return default(T);
        return (T)result;
    }
}

private void SomeMethod(string zipCode)
{
    var zipcode = ExecuteScalar<string>("select zipcode from Zipcodes where Zip = {0}", zipCode);
    ...
}

using System;

public class Program
{
    public static void Main()
    {
        Test t = new Test();
        t.WriteValue("abc");
    }
}

public class Test{
    private string teststring = "xyz";

    public void WriteValue(string teststring){

        Console.WriteLine(teststring);
        Console.WriteLine(this.teststring);
    }
}

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