{"id":74,"date":"2009-10-08T22:08:29","date_gmt":"2009-10-08T21:08:29","guid":{"rendered":"http:\/\/blog.rabihtawil.com\/?p=48"},"modified":"2009-10-08T22:08:29","modified_gmt":"2009-10-08T21:08:29","slug":"managing-bindingsource-position-in-data-driven-winforms","status":"publish","type":"post","link":"http:\/\/www.raytawil.com\/?p=74","title":{"rendered":"Managing BindingSource Position in Data Driven WinForms"},"content":{"rendered":"

If you are working with a Windows Form<\/span> where a user<\/span> can create and edit<\/span> data in the same form you may run into the problem of trying to set the BindingSource to\u00a0a given record in a DataSet you want to work with. <\/span><\/span><\/span><\/p>\n

For example let’s say you have a DataGridView<\/span> in a Smart Client<\/span>.\u00a0 When the\u00a0user<\/span> double clicks a given row in the <\/span><\/span>DataGridView<\/span> a\u00a0form opens so they can edit<\/span> the data.\u00a0 More times than not (no matter how many demos you watch) user’s do not edit<\/span> data values in DataGridViews.\u00a0 Although this is a supported feature, <\/span><\/span>business objects<\/span> are too complex.\u00a0 Imagine having to edit<\/span> a contact in a single row<\/span> in Outlook for example,\u00a0not fun and not very <\/span><\/span>user<\/span> friendly.\u00a0\u00a0Why every <\/span>Microsoft demo<\/span> I watch shows editing in DataGridViews is beyond me.\u00a0 I digress though.<\/span><\/span><\/p>\n

When the new form is instantiated we need to pass two things:\u00a0 the dataset we are working with, and the IDof the item we want to edit<\/span>.\u00a0 We can pass this information into the constructor of the form without any trouble as seen below. By passing in the DataSet\u00a0we can add new records, delete records or whatever\u00a0we need to do.\u00a0 The other benefit is since the dataset is passed by reference, any changes to\u00a0it will automatically appear in the row the <\/span>user<\/span> just double clicked on.\u00a0 In order for the form fields to be auto bound to the record the user<\/span> clicked on\u00a0we need to set the DataBinding of the controls\u00a0in the form to a\u00a0BindingSource.\u00a0 The BindingSource serves as <\/span>the go between<\/span> between the UI and data store.\u00a0\u00a0\u00a0 Here’s a sample “CellDoubleClick” event that would happen in the <\/span>DataGridView<\/span>:<\/span><\/p>\n

\n

1<\/span><\/span> int<\/span><\/span> id = Convert<\/span><\/span>.ToInt32(DataGridView<\/span><\/span><\/span><\/span>.Rows[e.RowIndex].Cells[0].Value);<\/p>\n

2<\/span><\/span> MyForm myForm = new<\/span><\/span> MyForm(dataSet, id);<\/p>\n

3<\/span><\/span> myForm.Show();<\/p>\n<\/div>\n

As the form loads the problem we face is\u00a0having to tell the BindingSource in the form which record we want to set as the BindingSource.Current<\/a> item.\u00a0 At first glance it looks like we would just get the DataRow and then set it as the Current property<\/span>.\u00a0 Wrong.\u00a0 The BindingSource.Current property<\/span> has only\u00a0a get accessor.\u00a0 Instead we need to use the <\/span>BindingSource.Position<\/a> property<\/span>.\u00a0\u00a0Note:\u00a0 Any change to the position property<\/span> updates the current property<\/span> used by the bindingsource.\u00a0\u00a0The problem we face now\u00a0is the\u00a0BindingSource.Position property<\/span> wants to know the <\/span>index<\/em> of the item in the underlying DataSource.<\/p>\n

We don’t know the index<\/span> value used by the BindingSource\u00a0but we do know the ID we want to use.\u00a0 This is where the <\/span>BindingSource.Find()<\/a> method comes in.\u00a0 Using the find method we can basically search the underlying datasource and retrieve the index<\/span> of a given item.\u00a0 Here’s an example:<\/span><\/p>\n

<\/span>contactBindingSource.Position = contactBindingSource.Find(“Id”, 2);<\/span><\/p>\n

Once the line above runs, it is going to search the column “Id” in the DataSource associated with the BindingSource and return the index<\/span> of that item. <\/span><\/p>\n

What if you use the same form to create a new item?\u00a0 Simple, call the BindingSource.AddNew()<\/a> method which will add a new item to the underlying DataSource.\u00a0 Then move the index<\/span> to the last item.\u00a0 Here’s a sample:<\/span><\/p>\n

bindingSource.AddNew();
\n<\/span> bindingSource.MoveLast();<\/span><\/p>\n

Since items are always added at the end of the associated data source the MoveLast() method\u00a0will set the index<\/span> to the last item in the underlying datasource.<\/span><\/span><\/p>\n

I hope this makes sense because it is an easy way to have a form bound to a DataSet and use the same form to perform “CRUD” operations with.<\/span><\/p>\n

<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

If you are working with a Windows Form where a user can create and edit data in the same form you may run into the problem of trying to set the BindingSource to\u00a0a given record in a DataSet you want to work with. For example let’s say you have a DataGridView in a Smart Client.\u00a0 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[110],"tags":[15,114,115,32,34,97],"_links":{"self":[{"href":"http:\/\/www.raytawil.com\/index.php?rest_route=\/wp\/v2\/posts\/74"}],"collection":[{"href":"http:\/\/www.raytawil.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.raytawil.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.raytawil.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.raytawil.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=74"}],"version-history":[{"count":0,"href":"http:\/\/www.raytawil.com\/index.php?rest_route=\/wp\/v2\/posts\/74\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.raytawil.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=74"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.raytawil.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=74"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.raytawil.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=74"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}