如何在时间内将“NULL”字分配给文本框（如果文本框为空）？

I have a problem in executing a SQL query from a C# tool where it tries to do the insert.

我在从C＃工具执行SQL查询时遇到问题，它尝试执行插入操作。

I need to insert NULL value if the string is empty (not entered by the user). I tried with the DB null value and normal string 'NULL' to do the NULL insert but all I get is an empty value (insetead of NULL keyword) which gives me the error.

如果字符串为空（我没有输入），我需要插入NULL值。我尝试使用DB null值和普通字符串'NULL'来执行NULL插入，但我得到的只是一个空值（不包括NULL关键字），这给了我错误。

Let me know if anyone has the solution for this....

让我知道是否有人有这个解决方案....

Below is my code

以下是我的代码

if (comboBox_ConfacValue.Text == "")
{
    comboBox_ConfacValue.Text = DBNull.Value.ToString();
}

if (combobox_conversionDescription.Text == "")
{
    combobox_conversionDescription.Text = "NULL";
}

try
{
    con.Open();

    if (MessageBox.Show("Do you really want to Insert these values?", "Confirm Insert", MessageBoxButtons.YesNo) == DialogResult.Yes)
    {
        SqlDataAdapter SDA = new SqlDataAdapter(@" insert INTO Table1 (alpha1,alpha2,alpha3)  VALUES ('" + comboBox_ConfacValue.Text + "','" + combobox_conversionDescription.Text + "','"+ combobox_Description.Text + "',')",con)

        SDA.SelectCommand.ExecuteNonQuery();
        MessageBox.Show("Inserted successfully.");
    }
}

1 个解决方案

#1

You should avoid this kind of code. Concatenating strings to produce an sql command is a recipe to disasters. Parsing errors is the common mistake, but a worse foe is lurking behind this pattern and is called Sql Injection

你应该避免这种代码。连接字符串以生成sql命令是灾难的一种方法。解析错误是常见的错误，但更糟糕的敌人隐藏在这种模式背后，称为Sql Injection

    try
    {
        con.Open();
        if (MessageBox.Show("Do you really want to Insert these values?", "Confirm Insert", MessageBoxButtons.YesNo) == DialogResult.Yes)
        {
            // Now the command text is no more built from pieces of 
            // of user input and it is a lot more clear
            SqlCommand cmd = new SqlCommand(@"insert INTO Table1 
                (alpha1,alpha2,alpha3)  
                VALUES (@a1, @a2, @a3)", con);
            // For every parameter placeholder add the respective parameter
            // and set the DbNull.Value when you need it
            cmd.Parameters.Add("@a1", SqlDbType.NVarChar).Value =
                string.IsNullOrEmpty(comboBox_ConfacValue.Text) ? 
                              DbNull.Value : comboBox_ConfacValue.Text);  

            cmd.Parameters.Add("@a2", SqlDbType.NVarChar).Value = 
                string.IsNullOrEmpty(combobox_conversionDescription.Text ) ? 
                              DbNull.Value : combobox_conversionDescription.Text );  

            cmd.Parameters.Add("@a3", SqlDbType.NVarChar).Value = 
                string.IsNullOrEmpty(combobox_Description.Text ) ? 
                              DbNull.Value : combobox_Description.Text );  

            // Run the command, no need to use all the infrastructure of
            // an SqlDataAdapter here....
            int rows = cmd.ExecuteNonQuery();

            // Check the number of rows added before message...
            if(rows > 0) MessageBox.Show("Inserted Successfully.");