[This topic is part of the Microsoft Azure Storage Client Library 1.7, which has been deprecated. See
Storage Client Library for the latest version.]
Returns an access condition such that an operation will be performed only if the resource's ETag value does not match the ETag value provided.
Namespace: Microsoft.WindowsAzure.StorageClient
Assembly: Microsoft.WindowsAzure.StorageClient (in Microsoft.WindowsAzure.StorageClient.dll)
Usage
Visual Basic |
---|
Dim etag As String
Dim returnValue As AccessCondition
returnValue = AccessCondition.IfNoneMatch(etag) |
Syntax
Visual Basic |
---|
Public Shared Function IfNoneMatch ( _
etag As String _
) As AccessCondition |
C# |
---|
public static AccessCondition IfNoneMatch (
string etag
) |
C++ |
---|
public:
static AccessCondition IfNoneMatch (
String^ etag
) |
Parameters
- etag
The ETag value to check.
Return Value
A structure specifying the
If-None-Match condition.
Example
The following example sets the if-none-match condition to upload a blob only if it does not already exist.
| Copy Code |
---|
static void UploadIfNotExist(Uri blobEndpoint, string accountName, string accountKey)
{
//Create service client for credentialed access to the Blob service.
CloudBlobClient blobClient = new CloudBlobClient(blobEndpoint, new StorageCredentialsAccountAndKey(accountName, accountKey));
//Get a reference to the blob.
CloudBlob blob = blobClient.GetBlobReference("mycontainer/myblob.txt");
//Specify the if-none-match condition.
BlobRequestOptions options = new BlobRequestOptions();
options.AccessCondition = AccessCondition.IfNoneMatch("*");
try
{
//Upload the blob only if it does not already exist.
blob.UploadText("Upload this blob if it does not already exist.", Encoding.UTF8, options);
}
catch (StorageClientException e)
{
if (e.ErrorCode == StorageErrorCode.BlobAlreadyExists)
{
Console.WriteLine("Blob was not uploaded because it already exists.");
}
else
{
Console.WriteLine(e.Message);
}
}
}
|
Remarks
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Platforms
Change History
See Also