---
title: "_bstr_t Class | Microsoft Docs"
ms.custom: ""
ms.date: "11/04/2016"
ms.technology: ["cpp-language"]
ms.topic: "language-reference"
f1_keywords: ["_bstr_t"]
dev_langs: ["C++"]
helpviewer_keywords: ["BSTR object", "_bstr_t class", "BSTR object [C++], COM encapsulation"]
ms.assetid: 58841fef-fe21-4a84-aab9-780262b5201f
author: "mikeblome"
ms.author: "mblome"
ms.workload: ["cplusplus"]
---
# _bstr_t Class
**Microsoft Specific**  
  
 A `_bstr_t` object encapsulates the [BSTR data type](http://msdn.microsoft.com/en-us/1b2d7d2c-47af-4389-a6b6-b01b7e915228). The class manages resource allocation and deallocation through function calls to **SysAllocString** and **SysFreeString** and other `BSTR` APIs when appropriate. The `_bstr_t` class uses reference counting to avoid excessive overhead.  
  
### Construction  
  
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|-|-|  
|[_bstr_t](../cpp/bstr-t-bstr-t.md)|Constructs a `_bstr_t` object.|  
  
### Operations  
  
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|-|-|  
|[Assign](../cpp/bstr-t-assign.md)|Copies a `BSTR` into the `BSTR` wrapped by a `_bstr_t`.|  
|[Attach](../cpp/bstr-t-attach.md)|Links a `_bstr_t` wrapper to a `BSTR`.|  
|[copy](../cpp/bstr-t-copy.md)|Constructs a copy of the encapsulated `BSTR`.|  
|[Detach](../cpp/bstr-t-detach.md)|Returns the `BSTR` wrapped by a `_bstr_t` and detaches the `BSTR` from the `_bstr_t`.|  
|[GetAddress](../cpp/bstr-t-getaddress.md)|Points to the `BSTR` wrapped by a `_bstr_t`.|  
|[GetBSTR](../cpp/bstr-t-getbstr.md)|Points to the beginning of the `BSTR` wrapped by the `_bstr_t`.|  
|[length](../cpp/bstr-t-length.md)|Returns the number of characters in the `_bstr_t`.|  
  
### Operators  
  
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|-|-|  
|[operator =](../cpp/bstr-t-operator-equal.md)|Assigns a new value to an existing `_bstr_t` object.|  
|[operator +=](../cpp/bstr-t-operator-add-equal-plus.md)|Appends characters to the end of the `_bstr_t` object.|  
|[operator +](../cpp/bstr-t-operator-add-equal-plus.md)|Concatenates two strings.|  
|[operator !](../cpp/bstr-t-operator-logical-not.md)|Checks if the encapsulated `BSTR` is a **NULL** string.|  
|[operator ==, !=, \<, >, \<=, >=](../cpp/bstr-t-relational-operators.md)|Compares two `_bstr_t` objects.|  
|[operator wchar_t* &#124; char\*](../cpp/bstr-t-wchar-t-star-bstr-t-char-star.md)|Extract the pointers to the encapsulated Unicode or multibyte `BSTR` object.|  
  
**END Microsoft Specific**  
  
## Requirements  
 **Header:** \<comutil.h>  
  
 **Lib:** comsuppw.lib or comsuppwd.lib (see [/Zc:wchar_t (wchar_t Is Native Type)](../build/reference/zc-wchar-t-wchar-t-is-native-type.md) for more information)  
  
## See Also  
 [Compiler COM Support Classes](../cpp/compiler-com-support-classes.md)