Marshal.StringToHGlobalAnsi Method

Copies the contents of a managed String into unmanaged memory, converting into ANSI format as it copies.

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

public static IntPtr StringToHGlobalAnsi(
	string s
)

Parameters

s
Type: System.String

A managed string to be copied.

Return Value

Type: System.IntPtr
The address, in unmanaged memory, to where s was copied, or 0 if s is null.

ExceptionCondition
OutOfMemoryException

There is insufficient memory available.

ArgumentOutOfRangeException

The s parameter exceeds the maximum length allowed by the operating system.

StringToHGlobalAnsi is useful for custom marshaling or when mixing managed and unmanaged code. Because this method allocates the unmanaged memory required for a string, always free the memory by calling FreeHGlobal. StringToHGlobalAnsi provides the opposite functionality of Marshal.PtrToStringAnsi.

This method copies embedded null characters, and includes a terminating null character.

The following example demonstrates how to convert the contents of a managed String class to unmanaged memory and then dispose of the unmanaged memory when done.

using System;
using System.Runtime.InteropServices;

class MainFunction
{
    static void Main()
    {
    Console.WriteLine("\nStringToGlobalAnsi\n");

    // Create a managed string.
    String  managedString = "I am a managed String";
    Console.WriteLine("1) managedString = " + managedString );

    // Marshal the managed string to unmanaged memory.
    IntPtr stringPointer = (IntPtr)Marshal.StringToHGlobalAnsi(managedString);
    Console.WriteLine("2) stringPointer = {0}", stringPointer );

    // Get the string back from unmanaged memory
    String RetrievedString = Marshal.PtrToStringAnsi( stringPointer);
    Console.WriteLine("3) Retrieved from unmanaged memory = " + RetrievedString );

    // Always free the unmanaged string.
    Marshal.FreeHGlobal(stringPointer);

    // IntPtr handle value is still the same:
    Console.WriteLine("4) stringPointer = " + stringPointer );

    // However, it contains no data after being freed:
    String RetrievedString2 = Marshal.PtrToStringAnsi( stringPointer);
    Console.WriteLine("5) RetrievedString2 = " + RetrievedString2 );
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

  • SecurityCriticalAttribute 

    requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Windows Phone 8.1, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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