文本框中的字段不正确时如何显示两个不同的消息框

Question

I need to display a message for two different textBoxes in my app if the information is entered incorrectly.

Basically when the user enters the information it will then search the database to check if that info is there. If it is not then it must display a message saying the entered information is incorrect

This is my code I am using

SqlConnection con = new SqlConnection(@"Data Source=DEVELOPMENT\ACCESSCONTROL;Initial Catalog=ACCESSCONTROL;User ID=sa;Password=P@55w0rd123");
SqlCommand check_User_Name = new SqlCommand("SELECT COUNT(*) FROM NewVisitor WHERE (IDNumber = @IDNumber AND PersonVisit = @PersonVisit)", con);
check_User_Name.Parameters.AddWithValue("@IDNumber", idNumber_TxtBox.Text);
check_User_Name.Parameters.AddWithValue("@PersonVisit", personVisiting_TxtBox.Text);
con.Open();

int UserExist = (int)check_User_Name.ExecuteScalar();

if (UserExist > 0)
{
      .....
}
else
{
    MessageBox.Show("No Visitor with ID Number: " + idNumber_TxtBox.Text + " Exists");

    MessageBox.Show("No Employee,  " + personVisiting_TxtBox.Text + " Exists");
}

At the moment it will only display the first messageBox if either information is entered incorrectly

Answer 1

You need to combine the two messages into a single string. Oh, and don't contatenate strings with a +, use string.Format or string interpolation ($)

var sb = new StringBuilder();
sb.AppendLine($"No Visitor with ID Number: {idNumber_TxtBox.Text} Exists");
sb.AppendLine($"No Employee, {personVisiting_TxtBox.Text} Exists");
MessageBox.Show(sb.ToString());

Answer 2

It's not possible to show two Message Boxes at the same time since the Message Box is a Modal window . So it will stop the execution of the MainWindow untill that first message box window is closed.

You could handle that by using a single message box with a combination of both messages.

string errorMessage = $"No Visitor with ID Number: {idNumber_TxtBox.Text} Exists") + Environment.NewLine + $"No Employee, {personVisiting_TxtBox.Text} Exists");
MessageBox.Show(errorMessage);