Adding a Computed Field to the LightSwitch Database
We can easily create new fields that derive their values from the values of other fields stored in a database for a LightSwitch application in Visual Studio 2012.
We can't include a computed field as part of a filter condition or sort term in a query. Also, we can't sort information in a screen by choosing the column heading of a computed field.
Step 1
Open the Solution Explorer.
Image 1
Step 2
In the Solution Explorer, double-click the table or right-click on it and select "Table" to open it.
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Step 3
The Table is shown in the Data Designer.
Image 3
Step 4
Choose the Computed Property option from the Command Bar in the Data Designer.
Image 4
Step 5
We will see that a new field is shown in the bottom row of the table.
Image 5
Step 6
In the Name column enter the Name (Total) and similarly in the Type column enter the Type (Decimal) for the new field.
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Step 7
Open the Property Window and choose the edit method link.
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Step 8
The Code Editor opens and generates a method named "Total_Compute".
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.LightSwitch;
namespace LightSwitchApplication
{
public partial class Emp1Tables
{
partial void Total_Compute(ref decimal result)
{
// Set result to the desired field value
result = this.Quantity * this.Price;
}
}
}