错误:索引不在数组的范围之内

i am getting an "Index was outside the bounds of the array." at dr1[1].ToString().

在dr1[1]. tostring()中，我得到一个“索引超出数组的边界”。

I have table contribution_master with 3 columns: type_id (int), name (varchar(20), amount (float). I want to extract all the amount rows.

表contribution_master包含3列:type_id (int)、名称(varchar(20)、金额(float))。我想提取所有的行。

SqlConnection SQLCon1 = new SqlConnection(ConfigurationManager.ConnectionStrings["PayrollConnStr"].ConnectionString.ToString());

    SqlCommand SQLCmd1 = new SqlCommand("SELECT amount FROM contribution_master", SQLCon1);

    try
    {
        SQLCon1.Open();
        SqlDataReader dr1 = SQLCmd1.ExecuteReader();
        while (dr1.Read())
        {
            employer_epf = Convert.ToDouble(dr1[0].ToString());
            employer_admin = Convert.ToDouble(dr1[1].ToString());
            employer_edli = Convert.ToDouble(dr1[2].ToString());
            employer_admin_edli = Convert.ToDouble(dr1[3].ToString());
            employer_esi = Convert.ToDouble(dr1[4].ToString());
        }
    }
    catch (SqlException ex)
    {
        string errorMessage = "Error ";
        errorMessage += ex.Message;
        lblWarn.Text = errorMessage;
        lblWarn.Visible = true;
    }
    finally
    {
        SQLCon1.Close();
    }

3 个解决方案

#1

The dr1[x] value relates to the position of the column it has read from the database.

dr1[x]值与它从数据库中读取的列的位置有关。

The SQL you specify SELECT amount FROM contribution_master will return the amount column, however the data in this can only be accessed either using dr1[0] or dr1["amount"].

您指定的从contribution_master中选择金额的SQL将返回金额列，但是其中的数据只能使用dr1[0]或dr1[“金额”]访问。

while (dr1.Read()) will iterate through each row of data in a loop until there is no more. However, if you need to access each row specifically, you might be better off filling the data into a datatable and assigning the values from there.

而(dr1.Read())将在循环中遍历每一行数据，直到没有其他数据为止。但是，如果您需要特定地访问每一行，您最好将数据填充到一个datatable中，并从该处分配值。

For example:

例如:

SqlDataAdapter da = new SqlDataAdapter(SQLCmd1);
DataTable dt = new DataTable();
da.Fill(dt);

employer_epf = Convert.ToDouble(dt.Rows[0][0].ToString());
employer_admin = Convert.ToDouble(dt.Rows[1][0].ToString());
employer_edli = Convert.ToDouble(dt.Rows[2][0].ToString());
employer_admin_edli = Convert.ToDouble(dt.Rows[3][0].ToString());
employer_esi = Convert.ToDouble(dt.Rows[4][0].ToString());

Hopefully this helps, but would it not be easier to have the axis of your table the other way around?

希望这能有所帮助，但如果将表格的轴反过来，会不会更容易呢?

#2

You're only returning one field from your query (amount) so there is only one field in the datareader (field 0)

您只从查询(数量)返回一个字段，因此datareader中只有一个字段(字段0)

Each call to datareader.Read() returns a single row. If you want subsequent rows, call Read() again.

每个对datareader.Read()的调用都返回一行。如果需要后续行，请再次调用Read()。

So, in your code...

因此,在您的代码…

if (dr1.Read())
{
    employer_epf = Convert.ToDouble(dr1[0].ToString()); 
    if (dr1.Read())
    {
        employer_admin = Convert.ToDouble(dr1[0].ToString()); 
        // etc...
    }
}

Or you can populate a DataTable that will return all the rows at once.

或者您可以填充一个DataTable，它将同时返回所有的行。

#3

Change SELECT statement. (You've select amount column from the table)

改变SELECT语句。(您已经从表中选择了amount列)

SELECT * FROM contribution_master

#1