Custom Control issues in Business Connecitvity Services

Question

Hi ,

I am working on a BCS project. I am required to create a custom control(DropDownList) for one of the columns in the external list that is being modeled using BDC Model in Visual Studio. I could create a custom control for the list

Here is the code for the custom control and part of the BDCM file.

Listing 1 : Custom Field Control

 

    public class GLAccountField : SPFieldText

    {

        public GLAccountField(SPFieldCollection fields, String fieldName) :

            base(fields, fieldName)

        { }

 

        public GLAccountField(SPFieldCollection fields, String typeName, String displayName) :

            base(fields, typeName, displayName)

        { }

 

        public override BaseFieldControl FieldRenderingControl

        {

            get

            {

                BaseFieldControl control = new GLAccountFieldControl();

                control.FieldName = this.InternalName;

                return control;

            }

        }

 

        public override string GetValidatedString(object value)

        {     …

            return base.GetValidatedString(value);

        }

    }

    public class GLAccountFieldControl : BaseFieldControl

    {

        protected DropDownList GLAccountSelector;

        protected override string DefaultTemplateName

        {

            get { return "GLAccountFieldControl"; }

        }

        public override object Value

        {

            get

            {

                EnsureChildControls();

                return this.GLAccountSelector.SelectedValue;

            }

            set

            {

                EnsureChildControls();

                this.GLAccountSelector.SelectedValue = (string)this.ItemFieldValue;

            }

        }

 

        protected override void CreateChildControls()

        {

            if (this.Field == null || this.ControlMode == SPControlMode.Display)

                return;

            base.CreateChildControls();

            this.GLAccountSelector =

                  (DropDownList)TemplateContainer.FindControl("GLAccountSelector");

            if (this.GLAccountSelector == null)

                throw new ConfigurationErrorsException("Error: cannot load .ASCX file!");

            if (!this.Page.IsPostBack)

            {

                this.GLAccountSelector.Items.AddRange(new ListItem[]

                {

                    new ListItem(string.Empty, null),

                    new ListItem("Mom and Pop Shop (1-20)", "1-20"),

                    new ListItem("Small Business (21-100)", "21-100"),

                    new ListItem("Medium-sized Business (101-1000)", "101-1000"),

                    new ListItem("Big Business (1001-20,000)", "1001-20000"),

                    new ListItem("Enterprise Business (over 20,000)", "20000+")

                });

            }

        }

  

Listing 2 : Part of BDCM file

…

<TypeDescriptor Name="associated_gl_id" TypeName="Sytem.Int32" DefaultDisplayName="GL Account" IsCollection="false">

  <Properties>

    <Property Name="SPCustomFieldType" Type="System.String">CustomControls.GLAccountField, MIMASBDCModel</Property>

  </Properties>

</TypeDescriptor>

…

associated_gl_id is an integer field in the database. With the above mentioned TypeDescriptor I get following two errors.

 

1. GLAccountField cannot be serialized. It needs a parameter less constructor. (I added one and passed null, null to the base constructor. Is this a correct thing to do?)
2.  Cannot convert Int32 to CustomControl.GLAccountField. It’s an IMetadataObectException. How do I fix this?

 

 

I have tested the control in Custom list and it is working as expected.

Could you please suggest a few corrections/improvements that would help me get over this problem.

Also would creating similar control help me display images in BCS list?

 

Thanks and Regards,

Zia

Answer 1

Hi, Zia

 

       According the error message, would you please try the following changes in your custom field type solution:

·         Try adding a overload constructor without any parameters

·         In your code snippet, the GLAccountFieldControl returns a string type value

-------------------------------------------------------------------

                public override object Value

                {

                    get

                    {

                         EnsureChildControls();

                         return this.GLAccountSelector.SelectedValue;

                   }

                  set

                  {

                       EnsureChildControls();

                       this.GLAccountSelector.SelectedValue = (string)this.ItemFieldValue;

                   }

                 }

 -------------------------------------------------------------------

               Would you please try converting it to Int32 type to match BCS field?

 

       Hope this can help!                                                                                                                              

        

Best Regards,

Aaron

Answer 2

Thanks Aaron. I'l try the things you've suggested.

I have tested the control in Custom list and it is working as expected. The issue with External list.

Also can you confirm that the TypeDescriptor for associated_gl_id is defined correctly?

Regards,

Zia