Struct ConditionStep
- Namespace
- DynaSharp
- Assembly
- DynaSharp.dll
A delete or a condition check in a transaction: what can follow it are its condition, the verbs of the next action, and sending. A check without a condition is rejected by DynamoDB. See TransactWriteExtensions for the rest.
public readonly ref struct ConditionStep : ITransactWriteStep<ConditionStep>, ITransactWriteChain<ConditionStep>, IConditional<ConditionStep>, IRetryable<ConditionStep>- Implements
- Inherited Members
- Extension Methods
Methods
If(ExpressionHandler)
Adds a condition in the grammar of DynamoDB, for what the conditions of handles do not cover. An interpolated Attr stands for an attribute name and any other interpolated value for a value. If it does not hold, the whole transaction is cancelled, and a second condition means both must hold.
public ConditionStep If(ExpressionHandler condition)Parameters
conditionExpressionHandlerThe condition.
Returns
- ConditionStep
The step, which replaces this one.
IfVersion(long)
Makes this action depend on the item having this version. If it has another, the whole transaction is cancelled, and the marker of this action says that this was the reason.
public ConditionStep IfVersion(long version)Parameters
versionlongThe version last read. A version of 0 stands for an item that does not exist, so it renders
attribute_not_existson the partition key. With Allow it stands for what reads as 0, an item without a version attribute or with 0 in it, or none.
Returns
- ConditionStep
The step, which replaces this one.
Remarks
A key does not carry a version, so a delete of an entity with a VersionAttribute needs this or IgnoreVersion(), and the next action throws InvalidOperationException without it. A condition check needs neither, and this makes it a check on the version. RetryOnConflictAsync<TResult>(Func<CancellationToken, ValueTask<TResult>>, CancellationToken) repeats a transaction together with the read of the version.
Exceptions
- ArgumentOutOfRangeException
versionis negative, or MaxValue.- InvalidOperationException
The table of this action has no VersionAttribute.
If<TCondition>(TCondition)
Adds a condition. If it does not hold, the whole transaction is cancelled, and a second condition means both must hold.
public ConditionStep If<TCondition>(TCondition condition) where TCondition : IConditionParameters
conditionTConditionThe condition.
Returns
- ConditionStep
The step, which replaces this one.
Type Parameters
TConditionThe type of the condition.
Exceptions
- ArgumentNullException
conditionis null.
IgnoreVersion()
Lets this delete go out without the check.
public ConditionStep IgnoreVersion()Returns
- ConditionStep
The step, which replaces this one.
MaxAttempts(int)
Sets the number of attempts of this call including the first, in place of MaxAttempts. A retry after a
lost response repeats a write that may have been applied, so 1 makes an ADD count at most once, and a lost response then reports a failure after the write was applied.
public ConditionStep MaxAttempts(int attempts)Parameters
attemptsintThe number of attempts.
Returns
- ConditionStep
The command, which replaces this one.
Exceptions
- ArgumentOutOfRangeException
attemptsis below 1.
ToRequestJson()
Renders the body this transaction would send, as DynamoDB JSON, without sending it. It ends the command, and is meant for tests and debugging. The text contains the items and a generated token that nothing ever sends.
public string ToRequestJson()Returns
- string
The request body.
Exceptions
- InvalidOperationException
The command was already sent, extended or rendered, or it has no action, which DynamoDB would reject.
Operators
implicit operator TransactWriteCommand(ConditionStep)
Hands the transaction on as a TransactWriteCommand, which is what a variable holds across a loop: tx = tx.Delete(table, key).IfExists();. This uses the step up like any
call on it, so the command is the one handle left, and a clause of the action can no longer follow. What the action still owes, such as a version, is checked by the next verb.
public static implicit operator TransactWriteCommand(ConditionStep step)Parameters
stepConditionStepThe step, which this replaces.
Returns
Exceptions
- InvalidOperationException
The step was already sent, extended or rendered.