如何通过可空字段查询 Azure Table 存储？
How to query Azure Table storage by nullable fields?
我有 table 个可以为 null 的字段：
public int? Order {get; set;}
public DateTime? StartDate {get; set;}
public DateTime? EndDate {get; set;}
public string Text {get; set;}
所有这些字段都可以是 NULL 值
查询记录时出现问题
其中 Order、StartDate、EndDate 和 Text 不为 NULL 或
其中 Order、StartDate 和 Text 不为空但 EndDate 为空或
其中 Order 和 Text 不为空，但 StartDate 和 EndDate 为空
Order.HasValue && StartDate.HasValue && EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && !StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text)
使用此类查询时出现错误或 400（错误请求）或不支持的运算符（不支持 isnullorempty）
根据这个答案 不可能查询 NULL 值...
据我所知，您无法将 DateTime 设置为 null 或空。
所以，我建议您可以将日期时间存储为字符串，当您想要映射到视图模型时，您可以将字符串转换为 DateTime。
插入实体时，将 DateTime 转换为字符串：
TableBatchOperation batchOperation = new TableBatchOperation();
DateTime dts = DateTime.Now;
DateTime dte = DateTime.UtcNow;
// Create a customer entity and add it to the table.
CustomerEntity customer1 = new CustomerEntity("Smith", "Jeff");
customer1.Order = 1;
customer1.StartDate = Convert.ToString(dts);
customer1.EndDate = Convert.ToString(dte);
customer1.Text = "text1";
// Create another customer entity and add it to the table.
CustomerEntity customer2 = new CustomerEntity("Smith", "Ben");
customer2.Order = 2;
customer2.StartDate = Convert.ToString(dts);
customer2.EndDate = "";
customer2.Text = "text2";
CustomerEntity customer3 = new CustomerEntity("Smith", "Cai");
customer3.Order = 3;
customer3.StartDate = "";
customer3.EndDate = "";
customer3.Text = "text3";
// Add both customer entities to the batch insert operation.
batchOperation.Insert(customer1);
batchOperation.Insert(customer2);
batchOperation.Insert(customer3);
// Execute the batch operation.
table.ExecuteBatch(batchOperation);
实体如下：
public class CustomerEntity : TableEntity
{
public CustomerEntity(string lastName, string firstName)
{
this.PartitionKey = lastName;
this.RowKey = firstName;
}
public CustomerEntity() { }
public int? Order { get; set; }
public string StartDate { get; set; }
public string EndDate { get; set; }
public string Text { get; set; }
public DateTime? ConvertTime(string dateStr)
{
if (string.IsNullOrEmpty(dateStr))
return null;
DateTime dt;
var convert=DateTime.TryParse(dateStr, out dt);
return dt;
}
}
显示或映射到模型时，可以使用ConvertTime方法判断列是否为空ConvertTime(entity.StartDate)。 如果为空，则显示为空，如果有值，则将字符串转换为日期时间。
string orderhasvalue = TableQuery.GenerateFilterCondition("Order", QueryComparisons.NotEqual, null);
string startdatehasvalue = TableQuery.GenerateFilterCondition("StartDate", QueryComparisons.NotEqual, null);
string enddatehasvalue = TableQuery.GenerateFilterCondition("EndDate", QueryComparisons.NotEqual, null);
string texthasvalue = TableQuery.GenerateFilterCondition("Text", QueryComparisons.NotEqual, null);
string startdatenothasvalue = TableQuery.GenerateFilterCondition("StartDate", QueryComparisons.Equal, null);
string enddatenothasvalue = TableQuery.GenerateFilterCondition("EndDate", QueryComparisons.Equal, null);
TableQuery<CustomerEntity> query1 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatehasvalue),
TableOperators.And, enddatehasvalue),
TableOperators.And, texthasvalue)
);
TableQuery<CustomerEntity> query2 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatehasvalue),
TableOperators.And, enddatenothasvalue),
TableOperators.And, texthasvalue)
);
TableQuery<CustomerEntity> query3 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatenothasvalue),
TableOperators.And, enddatenothasvalue),
TableOperators.And, texthasvalue)
);
// Print the fields for each customer.
foreach (CustomerEntity entity in table.ExecuteQuery(query2))
{
Console.WriteLine("{0}, {1}\t{2}\t{3}\t{4}\t{5}", entity.PartitionKey, entity.RowKey,
entity.Order, entity.ConvertTime(entity.StartDate), entity.ConvertTime(entity.EndDate), entity.Text);
}
您不能在 Azure Table 存储中查询空值，string 也不例外。写入 Azure table 时，具有空值的 属性 不会以表格形式存在，因此引用该 属性 的查询将始终 return 出乎意料的结果。作为解决方法，您可以做的是提供默认的非空值并查询这些值。如果 string 将值 "" 分配给 string，则允许您查询 string.Empty（不是 null，因为 "" 不是 null).对于 DateTime? 类型，同样的解决方法但不是 ""，您可以分配一个模糊的默认值，即。 DateTime.MinValue（或MaxValue）如果属性的实际值为null，否则您可以将其转换为string并将空字符串指定为默认值但您需要支付来回转换的价格，所以我个人更愿意尽可能避免这种情况。
您可以在 Azure table 存储上查询字符串数据类型字段的空过滤器。
OData 查询 = 不是（Id ne ''）
使用上面的 Odata 查询，您可以仅在字符串数据类型字段上过滤空数据。
您可以在 azure table storage Text Editor 中提供以上查询或使用下面是 C# 代码来获取数据
TableQuery partitionKeysQuery = new TableQuery()
.Where("不是 (Id ne '')");
List contentKeyEntities = new List();
TableQuerySegment partitionKeySegment = null;
while (partitionKeySegment == null || partitionKeySegment.ContinuationToken != null)
{
Task t1 = Task.Run(() => O365ReportingTable.ExecuteQuerySegmentedAsync(partitionKeysQuery, partitionKeySegment?.ContinuationToken));
t1.Wait();
partitionKeySegment = t1.Result;
contentKeyEntities.AddRange(partitionKeySegment.Results);
Console.WriteLine(contentKeyEntities.Count);
}
return contentKeyEntities；
public class 审计日志实体：表实体
{
#region构造函数代码
/// <summary>
/// default constructor
/// </summary>
public AuditLogEntity() { }
/// <summary>
/// constructor for creating an AuditLogEntity
/// </summary>
/// <param name="partitionKey">partition key of the data</param>
/// <param name="rowKey">row key for the row</param>
public AuditLogEntity(string partitionKey, string rowKey, JObject content)
{
PartitionKey = partitionKey;
RowKey = rowKey;
Properties = ConvertToEntityProperty(content);
}
#endregion Constructor Code
#region Public Properties
/// <summary>
/// additional properties for the entity
/// </summary>
public IDictionary<string, EntityProperty> Properties { get; set; }
#endregion Public Properties
#region Private Methods
/// <summary>
/// converts JObjects keys into properties
/// </summary>
/// <param name="content">JObject to convert</param>
/// <returns>Dictionary with key value pairs of JOjbect keys</returns>
private IDictionary<string, EntityProperty> ConvertToEntityProperty(JObject content)
{
IDictionary<string, EntityProperty> properties = new Dictionary<string, EntityProperty>();
if (content != null)
{
foreach (JProperty prop in content.Properties())
{
properties.Add(prop.Name, new EntityProperty(prop.Value.ToString()));
}
}
return properties;
}
/// <summary>
/// overrides the base WriteEntry to dynamically write properties to table storage
/// </summary>
/// <param name="operationContext">operation being performed</param>
/// <returns>dictionary of set properties</returns>
public override IDictionary<string, EntityProperty> WriteEntity(OperationContext operationContext)
{
IDictionary<string, EntityProperty> results = base.WriteEntity(operationContext);
foreach (string key in Properties.Keys)
{
results.Add(key, Properties[key]);
}
return results;
}
/// <summary>
/// overridden base ReadEntry method to convert propeties coming from table storage into the properties from this object
/// </summary>
/// <param name="properties">properties read in from table storage</param>
/// <param name="operationContext">operation being performed</param>
public override void ReadEntity(IDictionary<string, EntityProperty> properties, OperationContext operationContext)
{
base.ReadEntity(properties, operationContext);
Properties = properties;
}
#endregion Private Methods
}
我有 table 个可以为 null 的字段：
public int? Order {get; set;}
public DateTime? StartDate {get; set;}
public DateTime? EndDate {get; set;}
public string Text {get; set;}
所有这些字段都可以是 NULL 值
查询记录时出现问题
其中 Order、StartDate、EndDate 和 Text 不为 NULL 或
其中 Order、StartDate 和 Text 不为空但 EndDate 为空或
其中 Order 和 Text 不为空，但 StartDate 和 EndDate 为空
Order.HasValue && StartDate.HasValue && EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && !StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text)
使用此类查询时出现错误或 400（错误请求）或不支持的运算符（不支持 isnullorempty）
根据这个答案 不可能查询 NULL 值...
据我所知，您无法将 DateTime 设置为 null 或空。 所以，我建议您可以将日期时间存储为字符串，当您想要映射到视图模型时，您可以将字符串转换为 DateTime。
插入实体时，将 DateTime 转换为字符串：
TableBatchOperation batchOperation = new TableBatchOperation();
DateTime dts = DateTime.Now;
DateTime dte = DateTime.UtcNow;
// Create a customer entity and add it to the table.
CustomerEntity customer1 = new CustomerEntity("Smith", "Jeff");
customer1.Order = 1;
customer1.StartDate = Convert.ToString(dts);
customer1.EndDate = Convert.ToString(dte);
customer1.Text = "text1";
// Create another customer entity and add it to the table.
CustomerEntity customer2 = new CustomerEntity("Smith", "Ben");
customer2.Order = 2;
customer2.StartDate = Convert.ToString(dts);
customer2.EndDate = "";
customer2.Text = "text2";
CustomerEntity customer3 = new CustomerEntity("Smith", "Cai");
customer3.Order = 3;
customer3.StartDate = "";
customer3.EndDate = "";
customer3.Text = "text3";
// Add both customer entities to the batch insert operation.
batchOperation.Insert(customer1);
batchOperation.Insert(customer2);
batchOperation.Insert(customer3);
// Execute the batch operation.
table.ExecuteBatch(batchOperation);
实体如下：
public class CustomerEntity : TableEntity
{
public CustomerEntity(string lastName, string firstName)
{
this.PartitionKey = lastName;
this.RowKey = firstName;
}
public CustomerEntity() { }
public int? Order { get; set; }
public string StartDate { get; set; }
public string EndDate { get; set; }
public string Text { get; set; }
public DateTime? ConvertTime(string dateStr)
{
if (string.IsNullOrEmpty(dateStr))
return null;
DateTime dt;
var convert=DateTime.TryParse(dateStr, out dt);
return dt;
}
}
显示或映射到模型时，可以使用ConvertTime方法判断列是否为空ConvertTime(entity.StartDate)。 如果为空，则显示为空，如果有值，则将字符串转换为日期时间。
string orderhasvalue = TableQuery.GenerateFilterCondition("Order", QueryComparisons.NotEqual, null);
string startdatehasvalue = TableQuery.GenerateFilterCondition("StartDate", QueryComparisons.NotEqual, null);
string enddatehasvalue = TableQuery.GenerateFilterCondition("EndDate", QueryComparisons.NotEqual, null);
string texthasvalue = TableQuery.GenerateFilterCondition("Text", QueryComparisons.NotEqual, null);
string startdatenothasvalue = TableQuery.GenerateFilterCondition("StartDate", QueryComparisons.Equal, null);
string enddatenothasvalue = TableQuery.GenerateFilterCondition("EndDate", QueryComparisons.Equal, null);
TableQuery<CustomerEntity> query1 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatehasvalue),
TableOperators.And, enddatehasvalue),
TableOperators.And, texthasvalue)
);
TableQuery<CustomerEntity> query2 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatehasvalue),
TableOperators.And, enddatenothasvalue),
TableOperators.And, texthasvalue)
);
TableQuery<CustomerEntity> query3 = new TableQuery<CustomerEntity>().Where(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
TableQuery.CombineFilters(
orderhasvalue, TableOperators.And, startdatenothasvalue),
TableOperators.And, enddatenothasvalue),
TableOperators.And, texthasvalue)
);
// Print the fields for each customer.
foreach (CustomerEntity entity in table.ExecuteQuery(query2))
{
Console.WriteLine("{0}, {1}\t{2}\t{3}\t{4}\t{5}", entity.PartitionKey, entity.RowKey,
entity.Order, entity.ConvertTime(entity.StartDate), entity.ConvertTime(entity.EndDate), entity.Text);
}
您不能在 Azure Table 存储中查询空值，string 也不例外。写入 Azure table 时，具有空值的 属性 不会以表格形式存在，因此引用该 属性 的查询将始终 return 出乎意料的结果。作为解决方法，您可以做的是提供默认的非空值并查询这些值。如果 string 将值 "" 分配给 string，则允许您查询 string.Empty（不是 null，因为 "" 不是 null).对于 DateTime? 类型，同样的解决方法但不是 ""，您可以分配一个模糊的默认值，即。 DateTime.MinValue（或MaxValue）如果属性的实际值为null，否则您可以将其转换为string并将空字符串指定为默认值但您需要支付来回转换的价格，所以我个人更愿意尽可能避免这种情况。
您可以在 Azure table 存储上查询字符串数据类型字段的空过滤器。
OData 查询 = 不是（Id ne ''）
使用上面的 Odata 查询，您可以仅在字符串数据类型字段上过滤空数据。
您可以在 azure table storage Text Editor 中提供以上查询或使用下面是 C# 代码来获取数据
TableQuery partitionKeysQuery = new TableQuery() .Where("不是 (Id ne '')");
List contentKeyEntities = new List();
TableQuerySegment partitionKeySegment = null;
while (partitionKeySegment == null || partitionKeySegment.ContinuationToken != null)
{
Task
public class 审计日志实体：表实体 { #region构造函数代码
/// <summary>
/// default constructor
/// </summary>
public AuditLogEntity() { }
/// <summary>
/// constructor for creating an AuditLogEntity
/// </summary>
/// <param name="partitionKey">partition key of the data</param>
/// <param name="rowKey">row key for the row</param>
public AuditLogEntity(string partitionKey, string rowKey, JObject content)
{
PartitionKey = partitionKey;
RowKey = rowKey;
Properties = ConvertToEntityProperty(content);
}
#endregion Constructor Code
#region Public Properties
/// <summary>
/// additional properties for the entity
/// </summary>
public IDictionary<string, EntityProperty> Properties { get; set; }
#endregion Public Properties
#region Private Methods
/// <summary>
/// converts JObjects keys into properties
/// </summary>
/// <param name="content">JObject to convert</param>
/// <returns>Dictionary with key value pairs of JOjbect keys</returns>
private IDictionary<string, EntityProperty> ConvertToEntityProperty(JObject content)
{
IDictionary<string, EntityProperty> properties = new Dictionary<string, EntityProperty>();
if (content != null)
{
foreach (JProperty prop in content.Properties())
{
properties.Add(prop.Name, new EntityProperty(prop.Value.ToString()));
}
}
return properties;
}
/// <summary>
/// overrides the base WriteEntry to dynamically write properties to table storage
/// </summary>
/// <param name="operationContext">operation being performed</param>
/// <returns>dictionary of set properties</returns>
public override IDictionary<string, EntityProperty> WriteEntity(OperationContext operationContext)
{
IDictionary<string, EntityProperty> results = base.WriteEntity(operationContext);
foreach (string key in Properties.Keys)
{
results.Add(key, Properties[key]);
}
return results;
}
/// <summary>
/// overridden base ReadEntry method to convert propeties coming from table storage into the properties from this object
/// </summary>
/// <param name="properties">properties read in from table storage</param>
/// <param name="operationContext">operation being performed</param>
public override void ReadEntity(IDictionary<string, EntityProperty> properties, OperationContext operationContext)
{
base.ReadEntity(properties, operationContext);
Properties = properties;
}
#endregion Private Methods
}