Lightswitch Table Relationships
Dec 8, Microsoft Visual Studio LightSwitch is much like other. To make a relationship ( one to one) or (one to many) between tables, click on the. the couple you know who is breaking up like every other week. they are on and off all the time. COLOUR: AS SEEN IN IMAGE (Shades May Vary). MATERIAL: HIGH QUALITY VINYL. PACKAGE CONTENT: 1 x High Quality Vinyl Sticker. THE END RESULT .
LightSwitch generally detects the relation between two tables in DataSource and automatically establishes the same between the grids bound to the two tables. However, at times few developers often looks to manually control the relation. Core concept behind the implementation logic is to pass a parameter value to the Child table which is the current Row Index of the Parent Grid. With change in the Selected row index, new parameter value is passed to the Table query and the data is fetched again for the Child Grid.
While you use the above data link, you can select the tables 'Orders' and 'Order Details'. If you open the datasource designer for 'Order Details', you would notice that a relation has already been established by default. Refer to the image below. If we bind the above two datasources to separate grid controls, then they would automatically implement the Parent Child implementation. However, our objective is to implement this manually. So we have to create a new query from the child table 'Order Details' so that it does not have the relationship with the Parent Table 'Orders'.
Beginning LightSwitch Part 2: Feel the Love – Defining Data Relationships | Beth Massi
Apart from this we would have to create a parameter in the query which would act as a filter for the query result. The query details screen look like this in our LightSwitch application. So I won't go into the details. You can refer to the demo image below for reference.
Create a Local Parameter for the Screen Once we have the datasource, next step is to add a local Screen parameter which would be used to pass the value to the query table parameter. In LightSwitch, you can also specify the multiplicity as One to Zero or One which means that only a maximum of one related entity would be allowed.
For information on how to model a many-to-many relationship in LightSwitch see: How to Create a Many-to-Many Relationship You can also specify what happens to the email addresses when a contact is deleted. This means that a user would not be allowed to delete a Contact if they had any Email Addresses. Leaving the setting makes sense if we were working with Customers who had many Orders, for instance, but not in this case. The description at the bottom of the dialog is there to help you understand what you are doing when setting up the relationship.
Once you click OK you will see the relationship in the Data Designer which will show all direct relationships to the entity you are working with.
Beginning LightSwitch in VS 2013 Part 2: Feel the Love – Defining Data Relationships
Notice that a Contact property is now added to the EmailAddress entity. This is called a navigation property and represents the Contact to which the EmailAddress belongs. Double-click on the Contact entity to open it and you will notice a navigation property to all the EmailAddresses for that Contact.
Select the Email property and hit the Delete key. Alternatively you can right-click and choose Delete on the menu.
You might wonder why we need to create a new table separate from the EmailAddress. This is because an EmailAddress and a PhoneNumber are different aspects of a Contact and have no relation to each other except through the Contact itself. Therefore, we need to create a new table. Next add the relationship to Contact exactly the same way as before.
Last but not least, we need to create an Address table to store multiple physical addresses for a Contact. Set the AddressType and Address1 properties as required. Now set up the relationship for Address exactly as before. This makes sense in the case of Contact because if the user deletes the contact from the system all their information should be automatically deleted.
Keep in mind, however, that you may not want this behavior in other applications. For instance if you are building an order entry application you would want to restrict deletion of Customers if they had any Orders in the system in order to keep the Order history intact.
Now when we open the Contact entity in the Data Designer you can see all the direct relationships. Then drop down the Screen Data and select Contacts. Once you do this, you will see checkboxes for the additional related entities we created.
Select all of them and click OK. To build and launch the application hit F5.