Read Columns

Syntax

GetFields<TResult>(columns, filter, maxRows);

Arguments

columns	Expression<Func<T, TResult>>	Criteria by which the records of the repository should be filtered. This parameter must not be empty.
filter	Expression<Func<T, bool>>	Criteria by which the records of the repository should be filtered. This parameter must not be empty.	null
orderBy	Func<IQueryable, IOrderedQueryable>	Order in which the filtered records should be listed. This parameter is optional.	null
includeProperties	string	Navigation properties (recognized by the key word "virtual") that should be included. This parameter is optional.	""
maxRows	int?	Maximal number of records that should be filtered. This parameter is optional.	null

Description

Gets all the columns that are specified in the parameter columns from all the records of a repository that fulfill the criteria specified in the parameter filter.

If orderBy is not null, it first orders the records according to the attributes specified in the parameter orderBy before getting the columns from the newly ordered list.

If includeProperties is not null, it additionally loads the navigation properties that are specified in the parameter includeProperties. Navigation properties are "virtual" properties of the repository, i.e. they are not real properties and are accessed by navigating to another object. They would not get loaded unless specified in this parameter.

If maxRows is not 0, it makes sure that the number of filtered records does not exceed the specified number.

Example

Example 1: Reading only one specific column

The following program illustrates the function call with only one specified column:

var orderColumns = repo.GetFields(x => x.ProductID, 
                                  c => c.ProductID == "ADAM-567-BTO");

Function will load the column "ProductID" from the records of the repository that have "ADAM-567-BTO" as Production ID and store the result into the variable "orderColumns".

Example 2: Reading multiple columns

The following program illustrates the function call with three specified columns:

var orderColumns = repo.GetFields(x => new { x.ProductID, 
                                             x.ID, 
                                             x.Quantity }, 
                                  c => c.ProductID == "ADAM-567-BTO");

Function will load the columns "ProductID", "ID" and "Quantity" from the records of the repository that have "ADAM-567-BTO" as Production ID and store the result into the variable "orderColumns".

Example 3: Reading multiple columns with custom names

The following program illustrates the function call with three specified columns where two of them are given custom names:

var orderColumns = repo.GetFields(x => new { ProductName = x.ProductID, 
                                             OrderNumber = x.ID, 
                                             x.Quantity }, 
                                  c => c.ProductID == "ADAM-567-BTO");

Function will load the columns "ProductID", "ID" and "Quantity" from the records of the repository that have "ADAM-567-BTO" as Production ID and store the result into the variable "orderColumns", renaming the item "ProductionID" into "ProductName" and "ID" into "OrderNumber". The item "Quantity" maintains its name from the repository.

Example 4: Reading multiple columns and multiple filter criteria

var orderColumns = repo.GetFields(x => new { x.ProductID, 
                                             x.ID }, 
                                  c => c.ProductID == "ADAM-567-BTO"
                                    && c.Quantity > 10 
                                    && c.IsUrgent == true);

Function will load the columns "ProductID" and "ID" from the records of the repository that have "ADAM-567-BTO" as Production ID, have a Quantity of more than 10 and are Urgent, and store the result into the variable "orderColumns".

Example 5: Reading multiple columns with order + maximum limit

var orderColumns = repo.GetFields(x => new { x.ProductID, 
                                             x.ID }, 
                                  c => c.ProductID == "ADAM-567-BTO",
                                  o => o.OrderBy(t => t.Timestamp),  
                                  "",
                                  100);

Function will order the records by their Timestamp attribute, load the columns "ProductID" and "ID" from a maximum of 100 records of the ordered repository that have "ADAM-567-BTO" as Production ID and store the result into the variable "orderColumns".

Example 6: Reading multiple columns with order + maximum limit and including a virtual property

The following program illustrates the function call with multiple criteria, specified order, maximum limit and external property:

var orderList = repo.Get(x => x.ProductID == "ADAM-567-BTO" 
                           && c.Quantity > 10, 
                         o => o.OrderBy(c => c.Timestamp), 
                         "SapOrder",
                         100);

Function will order the records by their Timestamp attribute, load the columns "ProductID" and "ID" from a maximum of 100 records of the ordered repository that have "ADAM-567-BTO" as Production ID and a Quantity of more than 10, include the virtual property "SapOrder" (a navigation property of "Production Order") and store the result into the variable "orderList".