How are DataTextField and DataValueFields evaluated

Question

For a data bound control it is common scenario where we provide data text field and data value field ( in simple controls like Dropdownlist) but more fields in controls like Gridview. Generally the datasource is of type IEnumerable.

• How does the control internally process these values or rather how do they get the value from the data source without knowing what kind of datasource they are dealing with.

• Can someone explain with code how the controls evaluate these fields from the data source.

Answer 1

I never knew i could find this information so easily and LLyod was in fact wrong on using reflection to find data from a datasource. None of the data controls use it when i inspected through Reflector ;(

link that solved the problem

http://msdn.microsoft.com/en-us/library/ms366540.aspx

how you do it is below

protected override void PerformDataBinding(IEnumerable retrievedData)
        {
            base.PerformDataBinding(retrievedData);

            // Verify data exists.
            if (retrievedData != null)
            {

                string dataStr = String.Empty;

                foreach (object dataItem in retrievedData)
                {
                    if (DataTextField.Length > 0)
                    {
                        dataStr = DataBinder.GetPropertyValue(dataItem,
                            DataTextField, null);
                    }
                    else
                    {
                        PropertyDescriptorCollection props =
                                TypeDescriptor.GetProperties(dataItem);
                        if (props.Count >= 1)
                        {
                            if (null != props[0].GetValue(dataItem))
                            {
                                dataStr = props[0].GetValue(dataItem).ToString();
                            }
                        }
                    }
                }

            }
        }

If the above code seem Greek and Latin , you will have to have a course on asp.net controls development to understand what is being done.