在下面的示例中，我尝试使用Blob容器中的etags来确保我不会覆盖值。我希望第二次调用SetMetaDataAsync失败，因为我使用与原始请求相同的etag，但第二个请求成功完成。我已经通过查看门户网站验证了etag在第一次请求后发生了变化。
为什么第二个值在提交错误的etag时会覆盖第一个值？
var blobClient = account.CreateCloudBlobClient();
var container = blobClient.GetContainerReference("random-test");
container.CreateIfNotExistsAsync().GetAwaiter().GetResult();
container.FetchAttributesAsync().GetAwaiter().GetResult();
var etag = container.Properties.ETag;
container.Metadata["test"] = "foo";
container.SetMetadataAsync(AccessCondition.GenerateIfMatchCondition(etag), new BlobRequestOptions(), new OperationContext() { }).GetAwaiter().GetResult();
//uses the same etag as the first request but the etag on the container has changed now.
container.Metadata["test"] = "bar";
container.SetMetadataAsync(AccessCondition.GenerateIfMatchCondition(etag), new BlobRequestOptions(), new OperationContext() { }).GetAwaiter().GetResult();
答案 0 :(得分：1)
从这篇文章：
// [[Rcpp::depends(BH, bigmemory)]]
#include <bigmemory/MatrixAccessor.hpp>
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
void to_one(SEXP bm_addr) {
XPtr<BigMatrix> xptr(bm_addr);
MatrixAccessor<double> macc(*xptr);
for (size_t j = 0; j < macc.ncol(); j++)
for (size_t i = 0; i < macc.nrow(); i++)
if (macc[j][i] != 0) macc[j][i] = 1;
}
/*** R
library(bigmemory)
r <- 100
c <- 10000
bm <- matrix(sample(0:4, r * c, replace = TRUE), r, c)
bm <- as.big.matrix(bm, type = "double")
bm[, 1]
to_one(bm@address)
bm[, 1]
*/
操作仅支持Set Container Metadata条件标头。
答案 1 :(得分：1)
NuGet：Azure.Storage.Blobs
BlobClient blobClient = ...;
try {
var existingProperties = await blobClient.GetPropertiesAsync();
var etagCondition = new BlobRequestConditions() {
IfMatch = existingProperties.Value.ETag
};
await blobClient.UploadAsync(content, conditions: etagCondition);
} catch (RequestFailedException ex) when (ex.ErrorCode == BlobErrorCode.ConditionNotMet) {
// Todo: handle ETag mismatch
}