Q82. How to Update records in a table storage?

To update an entity, we use the Replace table operation. The first step is to retrieve the entity from the table and change the values to the required properties and perform the Replace operation.

  
//Retrieve the storage account from the connection string.
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
    CloudConfigurationManager.GetSetting("StorageConnectionString"));

//Create the table client
CloudTableClient tableClient = storageAccount.CreateCloudTableClient();

//Create the CloudTable object that represents the "items" table.
CloudTable table = tableClient.GetTableReference("items");

// Create a retrieve operation that takes an item entity.
TableOperation retrieveOperation = TableOperation.Retrieve<Item>("RawMaterial","R001");

// Execute the operation.
	TableResult retrievedResult = table.Execute(retrieveOperation);

We can also update an entity using Insert-or-Replace method.

Insert-or-Replace method

For the Replace operatin to be successful, we must retrieve the entity from the server. The problem with Replace operation is that sometimes we do not know whether the entity exists in the server and also the entity has been changed since it was retrieved. In such a scenario, the Replace operation will return an error and the Insert-or-Replace is useful. This operation inserts an entity if there is no entity and the entity is replaced even though update was made since we retrieved it.

  

// Retrieve the storage account from the connection string
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
    CloudConfigurationManager.GetSetting("StorageConnectionString"));

// Create the table client
CloudTableClient tableClient = storageAccount.CreateCloudTableClient();

// Create the CloudTable object that represents the "items" table
CloudTable table = tableClient.GetTableReference("items");

// Create a retrieve operation that takes a item entity
TableOperation retrieveOperation = TableOperation.Retrieve<Item>("RawMaterial", "R001");
//Execute the operation
TableResult retrievedResult = table.Execute(retrieveOperation);

// Assign the result to a Item object.
ItemEntity updateEntity = (ItemEntity)retrievedResult.Result;

if (updateEntity != null)
{
   //Change the description
   updateEntity.Description = "in nos";

   // Create the InsertOrReplace TableOperation
   TableOperation insertOrReplaceOperation = TableOperation.InsertOrReplace(updateEntity);

   // Execute the operation.
   table.Execute(insertOrReplaceOperation);
   Console.WriteLine("Entity was updated.");
}

---