Integration Services (SSIS) provides system variables and supports custom user variables. When you create a new package, add a container or a task to the package, or create an event handler, SSIS automatically includes a set of system variables for the item. System variables are always located in the System namespace. System variables contain useful information about the package and its containers, tasks, and event handlers. System variables contain information such as the name of the computer on which the package runs and the time the package starts. You can view the information that is contained in a system variable, but you cannot add to or update system variables.

You can also create custom variables for use in packages, containers, tasks, transformations, and precedence constraints. Custom variables can be created in the User namespace or a namespace of your choice. Custom variables can be used in the expressions that the For Loop container, the Derived Column transformation, the Conditional Split transformation, and precedence constraints may contain. For more information, see 在封裝中使用變數.

Every container in the SSIS object model has a Variables collection. This collection is accessible to each child of the container. A variable is accessed from the collection by using its name or its index. The Variables collection on a container represents an aggregation of the variables in the collection of its parent. The Variables collection of the Package class is visible to all objects in the package, providing a globally visible collection. Conversely, the variables contained in a task are limited in scope and visibility, and are only visible by the task.

重要事項：
The Variables is used with the Runtime classes. If you are using data flow components (Microsoft.SqlServer.Dts.Pipeline), you may be required to use the IDTSVariables100. To know which variables collection to use, see the documentation for the object you are acquiring variables on, and verify the return value.

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