INSERT INTO MySQL through C#

Question

I am making a WPF C# exc. I have a DAO class, with connection to my Database and also Service class, with some methods for getting information from Database. It works fine. But i want to insert to database also. So, where is my mistake? I have method in Service class with that code

public static DataTable createProject(string projectName, string depName, string empName, int estTime, DateTime startDate)
{
 string sql = "";
 sql += "INSERT INTO Projects (projectName, departmentName, employeeName, estimatedTime, startDate)";
 sql += "VALUES (" + projectName + depName + empName + estTime + startDate +")";
 return getDataTable(sql);
}

And after that, i am going to my xaml.cs

private void btnCreateAdd_Click(object sender, RoutedEventArgs e)
{
 Service.createProject((string)txtProjName.Text, (string)cmbCreateDepartment.SelectedItem, (string)cmbCreateEmployees.SelectedItem, Int32.Parse(txtElapseTime.Text), (DateTime)Calendar.SelectedDate);
}

It gives me some exeption in my xaml.cs

Unable to cast object of type 'System.Data.DataRowView' to type 'System.String'.

• Bruce: possible duplicate stackoverflow.com/questions/20346481/…
• NullReferenceException: In which line you are getting the exception, put a breakpoint and check
• Vladson: at Service.createProject() line

Answer 1

Look at the type of cmbCreateDepartment.SelectedItem and cmbCreateEmployees.SelectedItem attributes. It's a System.Data.DataRowView and not a String ! so the exception is logic.

Answer 2

Try this

private void btnCreateAdd_Click(object sender, RoutedEventArgs e)
{
Service.createProject((string)txtProjName.Text, ((ComboBoxItem)cmbCreateDepartment.SelectedItem).Content.ToString(), ((ComboBoxItem)cmbCreateEmployees.SelectedItem).Content.ToString(), Int32.Parse(txtElapseTime.Text), (DateTime)Calendar.SelectedDate);
}

• Vladson: Unable to cast object of type 'System.Data.DataRowView' to type 'System.Windows.Controls.ComboBoxItem'. This Exception
• NullReferenceException: @Vladson cmbCreateDepartment i hope this is ComboBox name.?
• NullReferenceException: @Vladson Then there is binding mistake.please go through this stackoverflow.com/questions/6420300/…
• Vladson: Now i have this error : There are more columns in the INSERT statement than values specified in the VALUES clause. The number of values in the VALUES clause must match the number of columns specified in the INSERT statement. But i have the right number of columns
• NullReferenceException: try using this sql = "INSERT INTO Projects VALUES('" + projectName +"','"+ depName +"','"+empName +"','"+ estTime +"','"+startDate +"')"