OutOfMemoryException Class


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The exception that is thrown when there is not enough memory to continue the execution of a program.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)


public class OutOfMemoryException : SystemException


Initializes a new instance of the OutOfMemoryException class.

System_CAPS_protmethodOutOfMemoryException(SerializationInfo, StreamingContext)

Initializes a new instance of the OutOfMemoryException class with serialized data.


Initializes a new instance of the OutOfMemoryException class with a specified error message.

System_CAPS_pubmethodOutOfMemoryException(String, Exception)

Initializes a new instance of the OutOfMemoryException class with a specified error message and a reference to the inner exception that is the cause of this exception.


Gets a collection of key/value pairs that provide additional user-defined information about the exception.(Inherited from Exception.)


Gets or sets a link to the help file associated with this exception.(Inherited from Exception.)


Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception.(Inherited from Exception.)


Gets the Exception instance that caused the current exception.(Inherited from Exception.)


Gets a message that describes the current exception.(Inherited from Exception.)


Gets or sets the name of the application or the object that causes the error.(Inherited from Exception.)


Gets a string representation of the immediate frames on the call stack.(Inherited from Exception.)


Gets the method that throws the current exception.(Inherited from Exception.)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions.(Inherited from Exception.)


Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetObjectData(SerializationInfo, StreamingContext)

When overridden in a derived class, sets the SerializationInfo with information about the exception.(Inherited from Exception.)


Gets the runtime type of the current instance.(Inherited from Exception.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Creates and returns a string representation of the current exception.(Inherited from Exception.)


Occurs when an exception is serialized to create an exception state object that contains serialized data about the exception.(Inherited from Exception.)

An OutOfMemoryException exception has two major causes:

  • You are attempting to expand a StringBuilder object beyond the length defined by its StringBuilder.MaxCapacity property.

  • The common language runtime cannot allocate enough contiguous memory to successfully perform an operation. This exception can be thrown by any property assignment or method call that requires a memory allocation. For more information on the cause of the OutOfMemoryException exception, see "Out of Memory" Does Not Refer to Physical Memory.

    This type of OutOfMemoryException exception represents a catastrophic failure. If you choose to handle the exception, you should include a catch block that calls the Environment.FailFast method to terminate your app and add an entry to the system event log, as the following example does.

    using System;
    public class Example
       public static void Main()
          try {
             // Outer block to handle any unexpected exceptions.
             try {
                string s = "This";
                s = s.Insert(2, "is ");
                // Throw an OutOfMemoryException exception.
                throw new OutOfMemoryException();
             catch (ArgumentException) {
                Console.WriteLine("ArgumentException in String.Insert");
             // Execute program logic.
          catch (OutOfMemoryException e) {
             Console.WriteLine("Terminating application unexpectedly...");
             Environment.FailFast(String.Format("Out of Memory: {0}",
    // The example displays the following output:
    //        Terminating application unexpectedly...

Some of the conditions under which the exception is thrown and the actions you can take to eliminate it include the following:

You are calling the StringBuilder.Insert method.

You are attempting to increase the length of a StringBuilder object beyond the size specified by its StringBuilder.MaxCapacity property. The following example illustrates the OutOfMemoryException exception thrown by a call to the StringBuilder.Insert(Int32, String, Int32) method when the example tries to insert a string that would cause the object's Length property to exceed its maximum capacity.

using System;
using System.Text;

public class Example
   public static void Main()
      StringBuilder sb = new StringBuilder(15, 15);
      sb.Append("Substring #1 ");
      try {
         sb.Insert(0, "Substring #2 ", 1);
      catch (OutOfMemoryException e) {
         Console.WriteLine("Out of Memory: {0}", e.Message);
// The example displays the following output:
//    Out of Memory: Insufficient memory to continue the execution of the program.

You can do either of the following to address the error:

Your app runs as a 32-bit process.

32-bit processes can allocate a maximum of 2GB of virtual user-mode memory on 32-bit systems, and 4GB of virtual user-mode memory on 64-bit systems. This can make it more difficult for the common language runtime to allocate sufficient contiguous memory when a large allocation is needed. In contrast, 64-bit processes can allocate up to 8TB of virtual memory. To address this exception, recompile your app to target a 64-bit platform. For information on targeting specific platforms in Visual Studio, see How to: Configure Projects to Target Platforms.

Your app is leaking unmanaged resources

Although the garbage collector is able to free memory allocated to managed types, it does not manage memory allocated to unmanaged resources such as operating system handles (including handles to files, memory-mapped files, pipes, registry keys, and wait handles) and memory blocks allocated directly by Windows API calls or by calls to memory allocation functions such as malloc. Types that consume unmanaged resources implement the IDisposable interface.

If you are consuming a type that uses unmanaged resources, you should be sure to call its IDisposable.Dispose method when you have finished using it. (Some types also implement a Close method that is identical in function to a Dispose method.) For more information, see the Using Objects That Implement IDisposable topic.

If you have created a type that uses unmanaged resources, make sure that you have implemented the Dispose pattern and, if necessary, supplied a finalizer. For more information, see the Dispose Pattern, Implementing a Dispose Method, and Object.Finalize topics.

You are attempting to create a large array in a 64-bit process.

By default, the common language runtime does not allow single objects whose size exceeds 2GB. To override this default, you can use the configuration file setting to enable arrays whose total size exceeds 2 GB.

You are working with very large sets of data (such as arrays, collections, or database data sets) in memory.

When data structures or data sets that reside in memory become so large that the common language runtime is unable to allocate enough contiguous memory for them, an OutOfMemoryException exception results.

To prevent the OutOfMemoryException exceptions, you must modify your application so that less data is resident in memory, or the data is divided into segments that require smaller memory allocations. For example:

  • If you are retrieving all of the data from a database and then filtering it in your app to minimize trips to the server, you should modify your queries to return only the subset of data that your app needs. When working with large tables, multiple queries are almost always more efficient than retrieving all of the data in a single table and then manipulating it.

  • If you are executing queries that users create dynamically, you should ensure that the number of records returned by the query is limited.

  • If you are using large arrays or other collection objects whose size results in an OutOfMemoryException exception, you should modify your application to work the data in subsets rather than to work with it all at once.

The following example gets a array that consists of 200 million floating-point values and then calculates their mean. The output from the example shows that, because the example stores the entire array in memory before it calculates the mean, an OutOfMemoryException is is thrown.

using System;
using System.Collections.Generic;

public class Example
   public static void Main()
      Double[] values = GetData();
      // Compute mean.
      Console.WriteLine("Sample mean: {0}, N = {1}",
                        GetMean(values), values.Length);

   private static Double[] GetData()
      Random rnd = new Random();
      List<Double> values = new List<Double>();
      for (int ctr = 1; ctr <= 200000000; ctr++) {
         if (ctr % 10000000 == 0)
            Console.WriteLine("Retrieved {0:N0} items of data.",
      return values.ToArray();

   private static Double GetMean(Double[] values)
      Double sum = 0;
      foreach (var value in values)
         sum += value;

      return sum / values.Length;
// The example displays output like the following:
//    Retrieved 10,000,000 items of data.
//    Retrieved 20,000,000 items of data.
//    Retrieved 30,000,000 items of data.
//    Retrieved 40,000,000 items of data.
//    Retrieved 50,000,000 items of data.
//    Retrieved 60,000,000 items of data.
//    Retrieved 70,000,000 items of data.
//    Retrieved 80,000,000 items of data.
//    Retrieved 90,000,000 items of data.
//    Retrieved 100,000,000 items of data.
//    Retrieved 110,000,000 items of data.
//    Retrieved 120,000,000 items of data.
//    Retrieved 130,000,000 items of data.
//    Unhandled Exception: OutOfMemoryException.

The following example eliminates the OutOfMemoryException exception by processing the incoming data without storing the entire data set in memory, serializing the data to a file if necessary to permit further processing (these lines are commented out in the example, since in this case they produce a file whose size is greater than 1GB), and returning the calculated mean and the number of cases to the calling routine.

using System;
using System.IO;

public class Example
   public static void Main()
      Tuple<Double, long> result = GetResult();
      Console.WriteLine("Sample mean: {0}, N = {1:N0}",
                        result.Item1, result.Item2);

   private static Tuple<Double, long> GetResult()
      int chunkSize = 50000000;
      int nToGet = 200000000;
      Random rnd = new Random();
      // FileStream fs = new FileStream(@".\data.bin", FileMode.Create);
      // BinaryWriter bin = new BinaryWriter(fs);
      // bin.Write((int)0);
      int n = 0;
      Double sum = 0;
      for (int outer = 0;
           outer <= ((int) Math.Ceiling(nToGet * 1.0 / chunkSize) - 1);
           outer++) {
         for (int inner = 0;
              inner <= Math.Min(nToGet - n - 1, chunkSize - 1);
              inner++) {
            Double value = rnd.NextDouble();
            sum += value;
            // bin.Write(value);
      // bin.Seek(0, SeekOrigin.Begin);
      // bin.Write(n);
      // bin.Close();
      return new Tuple<Double, long>(sum/n, n);
// The example displays output like the following:
//    Sample mean: 0.500022771458399, N = 200,000,000
You are repeatedly concatenating large strings.

Because strings are immutable, each string concatenation operation creates a new string. The impact for small strings, or for a small number of concatenation operations, is negligible. But for large strings or a very large number of concatenation operations, string concatenation can lead to a large number of memory allocations and memory fragmentation, poor performance, and possibly OutOfMemoryException exceptions.

When concatenating large strings or performing a large number of concatenation operations, you should use the StringBuilder class instead of the String class. When you have finished manipulating the string, convert the StringBuilder instance to a string by calling the StringBuilder.ToString method.

You pin a large number of objects in memory.

Pinning a large number of objects in memory for long periods can make it difficult for the garbage collector to allocate contiguous blocks of memory. If you've pinned a large number of objects in memory, for example by using the fixed statement in C# or by calling the GCHandle.Alloc(Object, GCHandleType) method with a handle type of GCHandleType.Pinned, you can do the following to address the OutOfMemoryException exception.

  • Evaluate whether each object really needs to be pinned,

  • Ensure that each object is unpinned as soon as possible.

  • Make sure that each call to the GCHandle.Alloc(Object, GCHandleType) method to pin memory has a corresponding call to the GCHandle.Free method to unpin that memory.

The following Microsoft intermediate (MSIL) instructions throw an OutOfMemoryException exception:

OutOfMemoryException uses the HRESULT COR_E_OUTOFMEMORY, which has the value 0x8007000E.

For a list of initial property values for an instance of OutOfMemoryException, see the OutOfMemoryException constructors.


The value of the inherited Data property is always null.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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