Marshal.StringToHGlobalAnsi(String) Method

Definition

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

C#
[System.Security.SecurityCritical]
public static IntPtr StringToHGlobalAnsi(string s);
C#
public static IntPtr StringToHGlobalAnsi(string? s);
C#
public static IntPtr StringToHGlobalAnsi(string s);

Parameters

s
String

A managed string to be copied.

Returns

IntPtr

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

Attributes

Exceptions

There is insufficient memory available.

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

Examples

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.

C#
using System;
using System.Runtime.InteropServices;
using System.Threading;

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, the data may be cleared after the memory is freed, depending on whether the memory allocated to stringPointer
        // has been reclaimed or not. Uncommenting the following line (Thread.Sleep(1000)) increases the likelihood of the memory being reclaimed.
        // Thread.Sleep(1000);
        String RetrievedString2 = Marshal.PtrToStringAnsi(stringPointer);
        Console.WriteLine("5) RetrievedString2 = " + RetrievedString2);
    }
}

Remarks

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.

Applies to

Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0

See also