Trying to return multiple values by passing single value in function in c#

I'm not that familiar with C#, but if you want to return multiple values in a single return statement, the only way to go is usually an array or an object. An array would be simplest in your case.

• The return type definition doesn't look like an array return type, try

private static string[] getDo() {...

• The return statement itself doesn't look like an array, try returning the values as an array

• You are defining variables inside the foreach-loop, which usually makes them unaccessible outside the loop. Try defining the variables outside the loop and use them in the loop.

I don't know if this is valid C#, but something like this:

private static String[] getDo(string DoNo)
    {           
        try
        {
            using (OracleConnection con = new OracleConnection(ConfigurationManager.ConnectionStrings["Oracle_To_Sql.Properties.Settings.Setting"].ToString()))
            {
                String[] toReturn = new String[2];
                string TVD_LS_NO, TVD_INV_NO;
                string query = "select SUBSTR(TVD_DO_ITEM_NO,'1','10') from T_VEHICLE_DTL1  where TVD_LS_NO=:TVD_LS_NO";
                OracleCommand myCommand = new OracleCommand(query, con);
                DataTable dt = new DataTable();
                OracleDataAdapter da = new OracleDataAdapter(myCommand);
                da.SelectCommand = new OracleCommand(query, con);                    
                da.Fill(dt);                    
                foreach (DataRow row in dt.Rows)
                {
                    TVD_LS_NO = row["TVD_LS_NO"].ToString();
                    TVD_INV_NO = row["TVD_INV_NO"].ToString();                        
                }
                toReturn[0] = TVD_LS_NO;
                toReturn[1] = TVD_INV_NO;
                return toReturn;
            }
        }
        catch (Exception ex)
        {

            throw;
        }

    }

Not sure if this will be the best answer, but I hope it will push you in the right direction.

There are a few concerns here, let's try to take them one by one.

• First of all, you say you want to return two values, but you are assigning them in a for loop, which could mean they will be assigned many times. Is this on purpose ? Or are you expecting the for loop to run only once ?

• Then, you declare your variables inside your for loop, which means they will be destroyed when you exit the loop, loosing their values and making the compiler angry (and sad).

• You are trying to use a return result syntax that is known by compilers since C# 7. If you are using a prior version, it will not work at all.

• Lastly, your try/catch is completely useless if you don't do something in your catch block, so you can remove it.

If I may suggest some additional understanding on TUples.

So, if we scratch it up in C# 7, it looks like this :

private static (string TVD_LS_NO, string TVD_INV_NO) getDo(string DoNo)
{
    //We declare our return value(s)
    var toReturn(TVD_LS_NO: "", TVD_INV_NO: "");

    using (OracleConnection con = new OracleConnection(ConfigurationManager.ConnectionStrings["Oracle_To_Sql.Properties.Settings.Setting"].ToString()))
    {
        string query = "select SUBSTR(TVD_DO_ITEM_NO,'1','10') from T_VEHICLE_DTL1  where TVD_LS_NO=:TVD_LS_NO";
        OracleCommand myCommand = new OracleCommand(query, con);
        DataTable dt = new DataTable();
        OracleDataAdapter da = new OracleDataAdapter(myCommand);
        da.SelectCommand = new OracleCommand(query, con);                    
        da.Fill(dt);                    

        foreach (DataRow row in dt.Rows)
        {
            //We assign our return values
            toReturn.TVD_LS_NO = row["TVD_LS_NO"].ToString();
            toReturn.TVD_INV_NO = row["TVD_INV_NO"].ToString();                        
        }

        return toReturn;
}

But that works only in C# 7

If you don't use C# 7, you have other possibilities :

1. Use ref keyword

   int value = 0;
   MyFunction(ref value);
   Console.WriteLine(value); //Outputs 10
   
   void MyFunction(ref int value)
   {
       value = 10;
   }
   

2. Use out keyword

   int value;
   MyFunction(value);
   Console.WriteLine(value); //Outputs 10
   
   void MyFunction(out int value)
   {
       value = 10;
   }
   

   To get the difference between the two, additional reading. You can use any number of ref/out parameters as you like.

3. Use a small class/structure (preferred way)

   public struct MyResultValues //could be public class MyResultValues
   {
       public int result1;
       public string result2;
   }
   
   MyResultValues result = MyFunction();
   Console.WriteLine(result.result1);
   Console.WriteLine(result.result2);
   
   public MyResultValues MyFunction()
   {
       MyResultValues toReturn = new MyResultValues();
       toReturn.result1 = 10;
       toReturn.result2 = "Hello World !";
       return toReturn;
   }