尝试从 Access 数据库中删除时出现 C# OleDb 异常“没有为一个或多个必需参数提供值”
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C# OleDb Exception "No value given for one or more required parameters" while trying to delete from Access database
提问by user2594788
I have a table with "SEMESTER, SUBJECT, OFFER, RESULT" where "SEMESTER" & "SUBJECT" is PRIMARY KEY. When i use the query
我有一个带有“学期、主题、报价、结果”的表格，其中“学期”和“主题”是主键。当我使用查询时
"DELETE FROM Course_Information WHERE Semester = 1 AND Subject = 'CSE-414' ;
"DELETE FROM Course_Information WHERE Semester = 1 AND Subject = 'CSE-414' ;
Its working perfectly in access database but i always get exception when i tried to use it in my c# code.
它在访问数据库中完美运行，但是当我尝试在我的 c# 代码中使用它时，我总是遇到异常。
Moreover its works if i use "DELETE FROM Course_Information WHERE Semester = 1 ;
此外，如果我使用“DELETE FROM Course_Information WHERE Semester = 1 ;
I want to use both "SUBJECT" & "SEMESTER" In the WHERE condition (Because there could be different subject in the same semester)
我想在 WHERE 条件中同时使用“SUBJECT”和“SEMESTER”（因为同一学期可能有不同的主题）
See my code,
看我的代码
connection_string = aConnection.return_connectionString(connection_string);
string sql_query = "DELETE FROM Course_Information WHERE Semester = " + this.textBox1.Text + " AND Subject = " + this.textBox2.Text + " ;";
OleDbConnection connect = new OleDbConnection(connection_string);
OleDbCommand command = new OleDbCommand(sql_query, connect);
try
{
connect.Open();
OleDbDataReader reader = command.ExecuteReader();
MessageBox.Show("Delete Successful!");
connect.Close();
UpdateDatabase();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
采纳答案by HansUp
Include the quotes around the value you get from this.textBox2.Textas in your working sample query.
this.textBox2.Text在您的工作示例查询中包含您从中获得的值周围的引号。
" AND Subject = '" + this.textBox2.Text + "';";
Imagine this.textBox2.Textcontains the text foo. Without adding those quotes in the WHEREclause the db engine would see ... WHERE Semester = 1 AND Subject = fooBut it can't find anything in the data source named foo, so assumes it must be a parameter. You need the quotes to signal the db engine it's a string literal value, 'foo'.
想象this.textBox2.Text包含文本foo。如果不在WHERE子句中添加这些引号，数据库引擎会看到... WHERE Semester = 1 AND Subject = foo但它在名为 的数据源中找不到任何内容foo，因此假定它必须是一个参数。您需要引号来通知数据库引擎它是一个字符串文字值'foo'。
Actually if you switch to a parameter query, you can avoid this type of problem because you won't need to bother with those quotes in the DELETEstatement. And a parameter query will also safeguard you against SQL injection. If a malicious user can enter ' OR 'a' = 'ain this.textBox2.Text, all rows in the table would be deleted.
实际上，如果您切换到参数查询，则可以避免这种类型的问题，因为您不需要打扰DELETE语句中的那些引号。并且参数查询还可以保护您免受 SQL 注入。如果恶意用户可以输入' OR 'a' = 'ain this.textBox2.Text，则表中的所有行都将被删除。
回答by AliMusa
If you got a same error for "insert" query you can use this method for avoid exception
如果“插入”查询出现相同的错误，您可以使用此方法来避免异常
string sqlQuery = "INSERT into EndResultOfTestCases(IDsOfCases,TestCaseName,ResultCase,ResultLog) VALUES(@ids, @casename, @results, @logs)";
connection = new OleDbConnection(connectionStringToDB);
command = new OleDbCommand(sqlQuery, connection);
command.Parameters.AddWithValue("@ids",IDs);
command.Parameters.AddWithValue("@casename", CaseName);
command.Parameters.AddWithValue("@results", resultOfCase);
command.Parameters.AddWithValue("@logs", logs);
connection.Open();
command.ExecuteNonQuery();
connection.Close();
}
