空文本框仍然在SQL Server中保存数据，即使表中的列也不允许为null

Question

我正面临这个问题，当我在所有文本框都为空时单击“保存”按钮时，它会在所有文本框上显示星标。 当我填写最后一个文本框而其他所有文本框都为空时，它会将数据保存到空字符串数据库中

我该如何处理这个问题？

if (tbIDCardNum.Text.Trim() == "")
{
    lblStarIDCardNum.Visibility = Visibility.Visible;
}

if (tbFirstName.Text.Trim() == "")
{
    lblStarFirstName.Visibility = Visibility.Visible;
}

if (rbMale.IsChecked == false && rbFemale.IsChecked == false)
{
    lblStarGender.Visibility = Visibility.Visible;
}

if (tbDOB.Text == "")
{
    lblStarDOB.Visibility = Visibility.Visible;
}

if (tbDateOfJoining.Text == "")
{
    lblStarDOJ.Visibility = Visibility.Visible;
}

if (tbEducation.Text.Trim() == "")
{
    lblStarEducation.Visibility = Visibility.Visible;
}

if (tbCNIC.Text.Trim() == "")
{
    lblStarCNIC.Visibility = Visibility.Visible;
}

if (tbSalary.Text.Trim() == "")
{
    lblStarSalary.Visibility = Visibility.Visible;
}

if (tbAddress.Text.Trim() == "")
{
    lblStarAddress.Visibility = Visibility.Visible;
}

if (tbEmail.Text.Trim() == "")
{
    lblStarEmail.Visibility = Visibility.Visible;
}

if (tbContact1.Text.Trim() == "")
{
    lblStarContact.Visibility = Visibility.Visible;
}
else
{
    try
    {
        conn.Open();

        cmd.CommandText = "insert into teacher (tIDCardNum, tFirstName, tLastName,tGender, tDOB, tCNIC, tEducation, tSalary, tJoinedOn, tAddress, tEmail, tContact1, tContact2, tContact3,tStatus) values ('" + tbIDCardNum.Text.Trim() + "' , '" + tbFirstName.Text.Trim() + "' , '" + tbLastName.Text.Trim() + "' , '" + gender + "' , '" + tbDOB.Text + "', '" + tbCNIC.Text + "' , '" + tbEducation.Text + "' , '" + tbSalary.Text.Trim() + "' , '" + tbDateOfJoining.Text.Trim() + "' , '" + tbAddress.Text.Trim() + "', '" + tbEmail.Text + "' , '" + tbContact1.Text + "' , '" + tbContact2.Text + "' , '" + tbContact3.Text + "',1)";

        cmd.Connection = conn;
        cmd.ExecuteNonQuery();

        cmd.Clone();
        conn.Close();

        HideStars();
        Refresh();

        MessageBox.Show("Saved");
   }
   catch (Exception ex)
   {
       if (ex.Message.Contains("Violation of PRIMARY KEY constraint "))
       {
           conn.Close();
           MessageBox.Show(ex.Message);
       }
       else
       {
           MessageBox.Show(ex.Message);
       }
   }
}

Answer 1

正如我所理解的那样，似乎主要问题是你检查不同if语句中的所有字段，但只有最后一个有其他字段。 正如我从你的帖子中假设的那样，这是你的问题; 你想让每个文本框都有一个值，然后才开始在数据库中插入它，对吗？

如果将代码分解成更可重用的东西，偶然清理一些东西，可以更好地解释这一点。

首先，通过引入你的类变量，我们可以用它来看看是否有任何空字段开始：

private bool HasEmptyFields = false;

接下来，让我们创建一个简单的帮助器，检查文​​本框是否为空/ null，更新相应标签的visiblity状态，如果确实为空则将'HasEmptyFields'设置为true：

private void ValidateField(TextBox textBox, Label label) {

    // check if the textbox actually is null - or empty (""), which is a difference
    // the nifty helper string.IsNullOrEmpty() will help with that
    var fieldIsEmpty = string.IsNullOrEmpty(textBox.Text.Trim());

    // next, based on if the field is empty,  set the visibility of the label
    // don't worry, this is fancy syntax for a simple if...then...else
    label.Visibility = fieldIsEmpty ? Visibility.Visible : Visibility.Hidden;

    if (fieldIsEmpty) {
        // ONLY if this field is actually null, or empty, we make sure to 
        // inform the rest of the code this occ
        HasEmptyFields = true;
    }
}

有了这个，我们可以做一些事情：

ValidateField(tbIDCardNum, lblStarIDCardNum);
ValidateField(tbFirstName, lblStarFirstName);
// etc... continue doing this for all you fields

if (HasEmptyFields) {
    // ONLY if there is any field detected as being empty/null
    // we simply stop here (and skip the insert-into-db stuff)
    return;
} 

try 
{
    // if all fields indeed have a value, let's
    // continue with the insert-into-db stuff here

    conn.Open();
    ...
} 

现在有一些方法可以让它变得更漂亮。 但这可能会帮助你朝着正确的方向前进。 另外值得一提的是一些其他注释，比如防止SQL注入 （必然会发生），以及查看数据验证工具，这样您就不必自己编写所有这些验证代码。 但显然，这不在这个答案的范围内。

Answer 2

如果您想要填写字段，那么您真的应该使用必填字段验证器 - 请参阅https://msdn.microsoft.com/en-us/library/5hbw267h%28VS.80%29.aspx?f=255&MSPPError = -2147217396