Unbound Columns

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This topic describes the main concepts of using unbound columns within the GridView extension.

Unbound Columns Overview

GridView supports both bound and unbound columns. Bound columns obtain their data from a data source. Unbound columns are not bound to any field in a data source. These columns can be populated manually by handling the GridViewSettings.CustomUnboundColumnData event or by specifying an expression via the GridViewDataColumn.UnboundExpression used to evaluate values for this field. The Expressions section describes the syntax for creating expressions.

There is no difference between working with bound and unbound columns. You can sort, group, display summaries and filter unbound columns in the same manner as bound columns.

An unbound column meets the following requirements.

Providing Data for Unbound Columns

ASP.NET MVC GridView provides two approaches to generate data for unbound columns.

  • Using an Unbound Expression

    To provide unbound columns with data using unbound expressions, compose the expression based on a specific syntax, and assign this expression to the GridViewDataColumn.UnboundExpression (via MVCxGridViewColumn.UnboundExpression) property.

    The code sample below demonstrates how to add an unbound column that retrieves its data using an unbound expression.

    Partial View code:

    
    @Html.DevExpress().GridView(settings => {
        settings.Name = "GridView";
        settings.CallbackRouteValues = new { Controller = "Home", Action = "GridViewPartial" };
        // ...
        // Add columns bound to model fields.
        settings.Columns.Add("FirstName");
        settings.Columns.Add("LastName");
        // Add an unbound column.
        settings.Columns.Add(column => {
            // "FieldName" contains a unique value that does not refer to any field in the GridView's data model. 
            column.FieldName = "FullName";
            // The column contains string values.
            column.UnboundType = DevExpress.Data.UnboundColumnType.String;
            // An unbound expression.
            column.UnboundExpression = "[FirstName]+' '+[LastName]";
        });
    }).Bind(Model).GetHtml()
    
  • Using a Delegate Method

    To provide unbound columns with data using a delegate method, assign this delegate method to the GridViewSettings.CustomUnboundColumnData property. The delegate method assigned to this property will be called for unbound columns only.

    The code sample below demonstrates how to add an unbound column that retrieves data using a delegate method.

    Partial View code:

    
    @Html.DevExpress().GridView(settings => {
        settings.Name = "GridView";
        settings.CallbackRouteValues = new { Controller = "Home", Action = "GridViewPartial" };
        // ...
        // Add columns bound to model fields.
        settings.Columns.Add("FirstName");
        settings.Columns.Add("LastName");
        settings.Columns.Add(column => {
            // "FieldName" contains a unique value that does not refer to any field in the GridView's data model. 
            column.FieldName = "FullName";
            // The column contains string values.
            column.UnboundType = DevExpress.Data.UnboundColumnType.String;
        });
        // A delegate method that allows you to generate data for an unbound column.
        settings.CustomUnboundColumnData = (s, e) => {
            if (e.Column.FieldName == "FullName") {
                string firstName = (e.GetListSourceFieldValue("FirstName")).ToString();
                string lastName = (e.GetListSourceFieldValue("LastName")).ToString();
                e.Value = firstName + " " + lastName;
            };
        };
    }).Bind(Model).GetHtml()
    

When the GridView extension is bound to a data source in Database Server Mode, you can only enable sorting, grouping, filtering and summary calculation for unbound columns that are populated with unbound expressions.

Limitations