I want to create Extension methods for dynamic type, but for some or the other reason i get error while compiling the code. below is my code sample The method which i am using is
public List<State> getStates()
{
return new List<State>(){
new State{StateID="1",StateName="Tamil Nadu"},
new State{StateID="2",StateName="Assam"},
new State{StateID="3",StateName="Andra"},
new State{StateID="4",StateName="bihar"},
new State{StateID="5",StateName="Bengal"},
};
}
and my extension method is
public static class helper
{
public static IEnumerable<SelectListItem> getIntoDropDownState(this List<dynamic> data,string textField,string valueField)
{
return data.Select(x => new SelectListItem
{
Text = x.textField,
Value = x.valueField
});
}
}
My compilation error which i get is
Compiler Error Message: CS1928: 'System.Collections.Generic.List' does not contain a definition for 'getIntoDropDownState' and the best extension method overload 'LearnAuthentication.Controllers.helper.getIntoDropDownState(System.Collections.Generic.List, string, string)' has some invalid arguments
I want to use the Extension method like this, and I am facing error
@Html.DropDownListFor(x => x.StateID, new LearnAuthentication.Controllers.Address().getStates().getIntoDropDownState("StateName", "StateID"), "Select State", 0)
can anyone help
That extension method in your example is not going to do what you describe. You could use reflection and generics.
public static class helper {
public static IEnumerable<SelectListItem> getIntoDropDownState<T>(this List<T> data, string textField, string valueField) where T : class {
var type = typeof(T);
var textPropertyInfo = type.GetProperty(textField);
var valuePropertyInfo = type.GetProperty(valueField);
return data.Select(x => new SelectListItem {
Text = (string)textPropertyInfo.GetValue(x),
Value = (string)valuePropertyInfo.GetValue(x)
});
}
}
Here is a unit test for the extension method
[TestClass]
public class MyTestClass {
[TestMethod]
public void MyTestMethod() {
//Arrange
var data = getStates();
//Act
var result = data.getIntoDropDownState("StateName", "StateID");
//Assert
Assert.IsNotNull(result);
var first = result.First();
Assert.AreEqual(data[0].StateName, first.Text);
Assert.AreEqual(data[0].StateID, first.Value);
}
public List<State> getStates() {
return new List<State>(){
new State{StateID="1",StateName="Tamil Nadu"},
new State{StateID="2",StateName="Assam"},
new State{StateID="3",StateName="Andra"},
new State{StateID="4",StateName="bihar"},
new State{StateID="5",StateName="Bengal"},
};
}
public class State {
public string StateID { get; set; }
public string StateName { get; set; }
}
}
Or you could forego reflection and use System.Web.Mvc.SelectList which does the heavy reflection lifting for you
public static class helper {
public static IEnumerable<System.Web.Mvc.SelectListItem> getIntoDropDownState<T>(this List<T> data, string textField, string valueField) where T : class {
return new System.Web.Mvc.SelectList(data, valueField, textField);
}
}
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