C# and sql database

Question

Hi,
I am new to programming and this forum as well. I am actually working on a windows application with C#. I have encountered a problem which I am not able to solve even after googling for 2 days. It might be a simple thing for all you experts.
I am trying to save the filepath in to the sql server table column. I have made this column of datatype nvarchar(max). This filepath is picked up by the openfiledialog object and then I have put it in a textbox. The insert query I am using in my data access layer is working just fine with other modules however this filepath is creating an error. Even if I assign the whole path to a string variable and pass that variable in to the query it still doesn't work. Here is my query   string sqlquery = "INSERT INTO [Costing] ([Date], [xlsdirectory], [xlsname], [xlsext],  [xls], [Amount]) VALUES ('" + date + "', '" + xlsdir + "', '" + xlsname + "', '" + xlsext + "' '" + @xls + "', '" + amount + "')";

I really need help. It would be greatly appreciated. Thanks in advance.