Implementation of Typed Method Delegates

• Feb 01, 2023
• 6 minutes to read

A call to a VerticalGrid view model’s VerticalGridModel.ProcessCustomBinding method in a Controller delegates the implementation of a VerticalGrid view model population to Model-layer functions specified with the method’s typed parameters. In general, the VerticalGridModel.ProcessCustomBinding method can accept four parameters that point to method delegates of specific types. This topic describes the available delegate types and provides you with information on how they can be implemented.

Implementation of the VerticalGridCustomBindingGetDataColumnCountHandler delegate

Method implementation is required.

Always implement this method to return the total number of data columns within your model, taking into account applied filtering (if any).

This method accepts the e parameter of the VerticalGridCustomBindingGetDataColumnCountArgs type, which provides you with the following arguments.

Name	Property	Description
DataColumnCount	VerticalGridCustomBindingGetDataColumnCountArgs.DataColumnCount	Gets or sets the total number of data columns within a custom model, taking into account the filtering applied within the VerticalGrid (if any).
FilterExpression	VerticalGridCustomBindingArgsBase.FilterExpression	Gets the filter condition currently applied to the VerticalGrid (if any filtering is used).
State	VerticalGridCustomBindingArgsBase.State	Gets an object containing information about the current state on the VerticalGrid.

When implementing this delegate, obtain the total number of columns in your model and assign it to the VerticalGridCustomBindingGetDataColumnCountArgs.DataColumnCount property. The VerticalGrid requires this information to properly calculate the number of pages to be displayed within the pager.

The returned total number should depend upon the filtering conditions (if they were applied to the VerticalGrid). Use the VerticalGridCustomBindingArgsBase.FilterExpression property to obtain the VerticalGrid’s filter expression and apply it to your model to obtain the proper number of rows that meet the filter condition. If no filtering is applied, the VerticalGridCustomBindingArgsBase.FilterExpression property returns an empty string.

The common procedure for implementation of this delegate is provided below.

• Filter your model (if filtering is used) using e.FilterExpression.
• Obtain the model’s total column count and return it to e.DataColumnCount.

Generally, the implementation will look as follows.

C#

public static void MyGetDataColumnCount(VerticalGridCustomBindingGetDataColumnCountArgs e) {
            e.DataColumnCount = Model
                .ApplyFilter(e.FilterExpression) //Your function that applies a filter to your model
                .Count(); //Return the total count of data columns in your model (taking into account the applied filtering, if any)
        }

Implementation of the VerticalGridCustomBindingGetDataHandler delegate

Method implementation is required.

Always implement this method to populate the VerticalGrid view model with data columns requested by the extension.

This method accepts the e parameter of the VerticalGridCustomBindingGetDataArgs type, which provides you with the following arguments.

Name	Property	Description
Data	VerticalGridCustomBindingDataArgsBase.Data	Gets or sets a list of currently requested model characteristics (depending upon which delegated method is being implemented, it can be a list of data columns, or a list of grouping information objects or a list of calculated summary values).
DataColumnCount	VerticalGridCustomBindingGetDataArgs.DataColumnCount	Gets the number of currently requested data columns to return.
FilterExpression	VerticalGridCustomBindingArgsBase.FilterExpression	Gets the filter condition currently applied to the VerticalGrid (if any filtering is used).
StartDataColumnIndex	VerticalGridCustomBindingGetDataArgs.StartDataColumnIndex	Gets the index of the first column in the requested column list.
State	VerticalGridCustomBindingArgsBase.State	Gets an object containing information about the current state on the VerticalGrid.

When implementing this delegate, return the requested data columns using the VerticalGridCustomBindingDataArgsBase.Data property.

The common procedure for the implementation of this delegate is provided below.

• Filter your model (if filtering is used) using e.State.FilterExpression.
• Sort your model (if sorting is used) using e.State.SortedRows.
• Obtain the number of columns specified by the e.DataColumnCount starting with e.StartDataColumnIndex, and return the obtained row list to e.Data.

Generally, the implementation will look as follows.

C#

public static void MyGetData(VerticalGridCustomBindingGetDataArgs e) {
            e.Data = Model
                .ApplyFilter(e.State.FilterExpression) //Your function that filters your model
                .ApplySorting(e.State.SortedRows) //Your function that sorts your model
                .Skip(e.StartDataColumnIndex) //Position on the first required data column
                .Take(e.DataColumnCount); //Get the number of currently requested data columns (columns of the current page or visible columns of the processed group)
        }

Implementation of the VerticalGridCustomBindingGetSummaryValuesHandler delegate

Method implementation is optional. It is required if you use summaries within the VerticalGrid.

Provide implementation for this method to calculate and return values of summaries required within the VerticalGrid, taking into account the applied filtering (if any).

This method accepts the e parameter of the VerticalGridCustomBindingGetSummaryValuesArgs type, which provides you with the following arguments.

Name	Property	Description
Data	VerticalGridCustomBindingDataArgsBase.Data	Gets or sets a list of currently requested model characteristics (depending upon which delegated method is being implemented, it can be a list of data columns, or a list of grouping information objects or a list of calculated summary values).
FilterExpression	VerticalGridCustomBindingArgsBase.FilterExpression	Gets the filter condition currently applied to the VerticalGrid (if any filtering is used).
State	VerticalGridCustomBindingArgsBase.State	Gets an object containing information about the current state on the VerticalGrid.
SummaryItems	VerticalGridCustomBindingGetSummaryValuesArgs.SummaryItems	Gets a list of summary items which are used within the VerticalGrid and whose values must be calculated.

When implementing this delegate, calculate values for summaries from the VerticalGridCustomBindingGetSummaryValuesArgs.SummaryItems collection, put the calculated summary values in a list, and return this list by setting the VerticalGridCustomBindingDataArgsBase.Data property.

The common procedure for the implementation of this delegate is provided below.

• Filter your model (if filtering is used) using e.State.FilterExpression.
• Traverse the e.SummaryItems list, calculate a summary value for each summary item, and return a list of the calculated values to e.Data.

In a general case, the implementation will look as follows.

C#

public static void MyGetSummaryValues(VerticalGridCustomBindingGetSummaryValuesArgs e) {
            var query = Model
                .ApplyFilter(e.State.FilterExpression); //Your function that filters your model
            var list = new ArrayList();
            foreach(var item in e.SummaryItems) {
                switch(item.SummaryType) {
                    case SummaryItemType.Count:
                        list.Add(query.Count());
                        break;
                    case SummaryItemType.Sum:
                        list.Add(query.Sum(item.FieldName));
                        break;
                }
            }
            e.Data = list;
        }

Implementation of the VerticalGridCustomBindingGetUniqueHeaderFilterValuesHandler delegate

Method implementation is optional. It is required if you display header filter buttons to use filtering within the VerticalGrid.

Provide implementation for this method to return unique values to be displayed in the header filter dropdown list invoked for a row.

This method accepts the e parameter of the VerticalGridCustomBindingGetUniqueHeaderFilterValuesArgs type, which provides you with the following arguments.

Name	Property	Description
Data	VerticalGridCustomBindingGetUniqueHeaderFilterValuesArgs.Data	Gets or sets a list of unique values contained within a specific data field.
FieldName	VerticalGridCustomBindingGetUniqueHeaderFilterValuesArgs.FieldName	Gets the name of the data field whose unique values should be returned.
FilterExpression	VerticalGridCustomBindingArgsBase.FilterExpression	Gets the filter condition currently applied to the VerticalGrid (if any filtering is used).
State	VerticalGridCustomBindingArgsBase.State	Gets an object containing information about the current state on the VerticalGrid.

When implementing this delegate, return a list of unique values obtained from a model data field (specified by the VerticalGridCustomBindingGetUniqueHeaderFilterValuesArgs.FieldName property) to the VerticalGridCustomBindingDataArgsBase.Data property. You may also need to take into account the applied filter condition, which can be obtained using the e.FilterExpression (VerticalGridCustomBindingArgsBase.FilterExpression) or e.State.FilterExpression.

The common procedure for implementation of this delegate is provided below.

• Filter your model (if filtering is used) using e.FilterExpression.
• Obtain a list of unique values from a data field specified by e.FieldName and return this list to e.Data.

In most cases, the implementation will look as follows.

C#

public static void MyGetUniqueHeaderFilterValues(VerticalGridCustomBindingGetUniqueHeaderFilterValuesArgs e) {
            e.Data = Model
                .ApplyFilter(e.FilterExpression) //Your function that filters your model
                .GetUniqueValues(e.FieldName); //Your function that obtains unique values of the specified data field
        }