c# - 参数化查询需要 C# SQL 未提供的参数

Question

我是 SQL 和 C# 新手，遇到了此 SQL 错误。

The parameterized query '(@pid nvarchar(4000),@desc nvarchar(4000),@cat nvarchar(4000),@p' expects the parameter '@pid', which was not supplied.

我真的需要帮助。谢谢!

 public void InsertRecord()
    {
        SqlCommand cmd = new SqlCommand("INSERT INTO PRODUCTS VALUES (@pid, @desc, @cat, @price, @scode)", myCon);
        cmd.Parameters.AddWithValue("@pid", productID);
        cmd.Parameters.AddWithValue("@desc", description);
        cmd.Parameters.AddWithValue("@cat", category);
        cmd.Parameters.AddWithValue("@price", price);
        cmd.Parameters.AddWithValue("@scode", supplierCode);//corrected the "key codes"

        myCon.Open();
        cmd.ExecuteNonQuery();
        myCon.Close();//added these lines of codes
    }

Answer 1

您必须检查每个参数是否为空。如果是，您必须传递DBNull.Value。

SqlParameter pidParam = command.Parameters.AddWithValue("@pidParam", productID);
if (productID == null)
{
    pidParam.Value = DBNull.Value;
}

来源:The parameterized query ..... expects the parameter '@units', which was not supplied