C# Error Message - CS1502: The best overloaded method match for 'string.IsNullOrEmpty(string)' has some invalid arguments

Question

_{Tuesday, August 19, 2008 2:34 PM}

 

I am using the AJAX Cascading Style Menu code that was given in this example:  http://www.asp.net/AJAX/AjaxControlToolkit/Samples/CascadingDropDown/CascadingDropDown.aspx  (If you click on the "watch video" link, there is a link to download the code also).  I had to change the C# code a little bit because I have my dropdown menus within a form, so I changed the C# code to find the controls in the form.  The problem I am having is that when I try to run this code, I get the error message:  CS1502: The best overloaded method match for 'string.IsNullOrEmpty(string)' has some invalid arguments.  The error calls out this line of code:  if (string.IsNullOrEmpty(make))    

 What is wrong with that code?

Thanks,

Mary 

 

using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using System.Web.Services;

using System.Collections.Specialized;

using AjaxControlToolkit;

public partial class Nanny_NannyMembers_temp : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)

{

 

 

// Get selected values

DropDownList make = (DropDownList)FormView1.FindControl("DropDownList1");

DropDownList model = (DropDownList)FormView1.FindControl("DropDownList2");

DropDownList color = (DropDownList)FormView1.FindControl("DropDownList3");

 

 

// Output result string based on which values are specified

if (string.IsNullOrEmpty(make))

{

Label1.Text = "Please select a make.";

}

else if (string.IsNullOrEmpty(model))

{

Label1.Text = "Please select a model.";

}

else if (string.IsNullOrEmpty(color))

{

Label1.Text = "Please select a color.";

}

else

{

Label1.Text = string.Format("You have chosen a {0} {1} {2}. Nice car!", color, make, model);

}

}

[WebMethod]

[System.Web.Script.Services.ScriptMethod]

public static CascadingDropDownNameValue[] GetDropDownContentsPageMethod(string knownCategoryValues, string category)

{

return new CarsService().GetDropDownContents(knownCategoryValues, category);

}

 

}

All replies (2)

_{Tuesday, August 19, 2008 2:42 PM ✅Answered}

"make" is typed as a DropDownList, not a String. Therefore, it cannot be used with the String.IsNullOrEmpty method.

Instead, simple check to see if "make" is null.

if (make == null)

---

_{Tuesday, August 19, 2008 2:51 PM}

Thank you!  That worked!