Why is Console.Readline not executing as expected
Solution 1
The problem is the use of the problematic method Console.Read()
. This method will block until a full line of text is entered, but it only returns the first character, leaving the remaining text in the input buffer. The carriage return that was used to enter the first value and unblock the read operation is still sitting in the input buffer when the Console.ReadLine()
operation is performed. Consequently, a blank line is returned.
I recommend that you replace Console.Read().ToString()
with Console.ReadLine()
to fix this problem.
The problem can be demonstrated with this code:
static void Main(string[] args)
{
string value = Console.Read().ToString();
Console.WriteLine("You entered: {0}", value);
Console.WriteLine("Press ENTER to continue...");
Console.ReadLine(); // Returns immediately.
Console.WriteLine("Continuing....");
}
And fixed like this:
string value = Console.ReadLine();
Solution 2
Is your project configured as a console application? It needs to be built with different switches in order to set the flags in the exe file so that the OS loader will know that it needs to create a console window for the process. GUI apps don't set that flag, and don't get a console window.
In VS2010, right click on your project's Properties link, click on the Application tab, and change Output Type from Windows Application to Console Application. Rebuild and run.
Kobojunkie
I am a dedicated Developer at heart coding and pushing my way to becoming a master. Would really appreciate if you those who are not willing to share their knowledge, without question, avoid even posting a responses to questions asked. Some of us are here to learn from those who have know.
Updated on June 06, 2022Comments
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Kobojunkie about 2 years
I have the following code below to work with. The problem I have here is that the code runs through the while loop without waiting for input on the line String temp = Console.ReadLine() . Need help understanding why and how to fix please. Thanks in advance!
/*Banker's algorithm Implementation*/ class Program { static void Main(string[] args) { int n = 0;//number of resources we will be dealing with int proc_num = 0;//Total number of processes to share available resources IDictionary<String, SysProcess> processes = new Dictionary<String, SysProcess>(); IDictionary<String, int> MaxR = new Dictionary<String, int>();// maximum available resources IDictionary<String, int> avail = new Dictionary<String, int>();// Available resources after first allocation Dictionary<String, int> availsum = new Dictionary<string, int>(); //Start while (true) { Console.WriteLine(" What is number of resources to be shared? : "); if (!int.TryParse(Console.ReadLine(), out n)) { Console.WriteLine(" Error Please provide valid number --- {0}!", n); } else { break; } } //get the maximum number of each Resources Ie Total Resources Available while (true && n>0) { Console.WriteLine("Using a comma delimited list(e.g. 0, 0, 0, 0) list maximum of each of the {0} resources : ", n); String temp; temp = Console.ReadLine(); if (!String.IsNullOrEmpty(temp)) { String[] maxR = temp.Split(','); for (int a = 1; a <= n; a++) { MaxR.Add("Resource#" + a.ToString(), Convert.ToInt32(maxR[a])); } break; } } while (true && n>0) { Console.Write("Enter total number of processes to share the available resources :"); if (!int.TryParse(Console.Read().ToString(), out proc_num)) { Console.WriteLine(" Error Please provide valid number --- {0}!", proc_num); } else { break; } } if(proc_num > 0) { //Request Process Max and allocated resources data for (int i = 1; i <= proc_num; i++) { Console.Write("Using a comma delimited list, Enter total number of Resources 1 through {0} are needed by PROCESS#{1} ?", n, i); String[] temps = Console.ReadLine().Split(','); SysProcess tempproc = new SysProcess("Process#" + i.ToString()); for (int a = 0; a < temps.Length; a++) { tempproc.Add_max_resource("Resource#" + (a + 1).ToString(), Convert.ToInt32(temps[a])); } //How many resources have already been allocated to each resource temps = null; Console.Write("Using a comma delimited list,Enter number of resources 1 through {0} already allocated to PROCESS#{1} ? ", n, i); temps = Console.ReadLine().Split(','); for (int a = 0; a < temps.Length; a++) { tempproc.add_alloc_resource("Resource#" + (a + 1).ToString(), Convert.ToInt32(temps[a])); } processes.Add("Process#" + i.ToString(), tempproc); } Console.WriteLine("Processing . . . "); Console.WriteLine(); Console.WriteLine("Available resources "); //Compute Available Resources for (int i = 0; i < n; i++) { if (!availsum.ContainsKey("Resource#" + (i + 1).ToString())) availsum.Add("Resource#" + (i + 1).ToString(), 0); foreach (SysProcess sp in processes.Values) { //add sum up the available availsum["Resource#" + (i + 1).ToString()] += sp.alloc_resources["Resource#" + (i + 1).ToString()]; } } //print out the availables we computed Console.Write(" avail< "); for (int j = 0; j < n; j++) { Console.Write(availsum["Resource#" + (j + 1).ToString()] + ","); if (j + 1 == n)//if this is the last one, go ahead and output the rest Console.Write("{0} > ", availsum["Resource#" + (j + 1).ToString()]); } // Printing resources still needed Console.WriteLine(); foreach (SysProcess p in processes.Values) { p.print_needed(); } //a) Find a row in the Need matrix which is less than the Available vector. //If such a row exists, then the process represented by that row may complete //with those additional resources. If no such row exists, eventual deadlock is possible. Dictionary<String, int> _currentavailsum; foreach (SysProcess p in processes.Values) { int TotalSproccounter = 0; String safelead; if (isprocessSafe(n, p, availsum)) { TotalSproccounter++; safelead = p.id; _currentavailsum = new Dictionary<String, int>(); _currentavailsum = availsum;//get a copy of the original data to begin with foreach (SysProcess q in processes.Values) { if (q != p)//we only want to compare with the others from here { if (isprocessSafe(n, p, _currentavailsum)) { update_availsum(n, q, ref _currentavailsum);//update the currentavail count TotalSproccounter++; //update print safelead += ", " + q.id; } } } if (TotalSproccounter == proc_num) { Console.WriteLine("Safe allocation < {0} >", safelead); } else { Console.WriteLine("Deadlock reached/unsafe allocation : < {0} >", safelead); } } } } Console.ReadLine(); } //compares the number of resources needed against the number of resources available public static Boolean isprocessSafe(int n, SysProcess p, IDictionary<String, int> avail) { int safecount = 0; foreach (String resourcekey in avail.Keys) { if (p.need_resources.ContainsKey(resourcekey) && p.need_resources[resourcekey] <= avail[resourcekey]) { safecount++; } } if (safecount == n) { return true; } return false; } //compares the number of resources needed against the number of resources available public static void update_availsum(int n, SysProcess p, ref Dictionary<String, int> _currentavailsum) { foreach (String resourcekey in _currentavailsum.Keys) { if (p.need_resources.ContainsKey(resourcekey)) { _currentavailsum[resourcekey] += p.need_resources[resourcekey]; } } } } //container class for processes public class SysProcess { public String id { get; set; } Dictionary<String, int> _max_resources = null; // will hold the Resource name and the the number of resources Dictionary<String, int> _alloc_resources = null;//allocated resources Dictionary<String, int> _need_resources = null;//allocated resources public Dictionary<String, int> max_resources { get { return _max_resources; } } public Dictionary<String, int> alloc_resources { get { return _alloc_resources; } } public Dictionary<String, int> need_resources { get { return _need_resources; } } public SysProcess(String procID) { _max_resources = new Dictionary<String, int>(); _alloc_resources = new Dictionary<String, int>(); id = procID; } public void Add_max_resource(String resource, int count) { _max_resources.Add(resource, count); } public void add_alloc_resource(String resource, int count) { _alloc_resources.Add(resource, count); _need_resources.Add(resource, _max_resources[resource] - alloc_resources[resource]); } public void print_needed() { Console.Write(id); foreach (int s in _need_resources.Values) { Console.Write(" {0}", s); } } }
Probably a good idea to add the whole code here since I am still unable to figure this one out. Please help