Format datetime and decimal in a webgrid

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C#

MVC

WebGrid

I'm populating an MVC WebGrid with data from a schema which is unknown at design time. It's all working fine, although I'm struggling with formatting the data. I just don't know the syntax to set a property of type Func<object, object>.

In the controller

var fields = GetListOfFieldsFromDB();
foreach (var f in fields)
{
    var c = new System.Web.Helpers.WebGridColumn();
    c.ColumnName = f.FieldName;
    c.Header = f.FieldAlias;
    c.CanSort = true;
    switch (f.SqlDataType)
    {
        case "datetime":
            c.Format = (item) => string.Format("{0:dd MMM yyyy}", 
                             item.DontKnowTheNameOfTheFieldYet; // Need help here . 
            break;

        case "decimal":
            c.Format = item => item.ToString("C"); // Need more help here. 
                                                   // No clue what the syntax should be.
            break;

         // some more formats here
         ...
     }

   columnList.Add(c);
}

In the view

var grid = new WebGrid(source: Model.Records, canPage: true, rowsPerPage: 20);
@grid.GetHtml(tableStyle: "table", columns: Model.Columns)

What I have tried:

c.Format = item => item.ToString("C"); //doesn't work