带有3个AND条件的c#查询

我有3个组合框，从MS Access数据库中获取信息。我要根据组合框的值从数据库中选择数据。

我写了这个查询:

string query = "select * from products where category='" + comboBox1.Text + "' and subcategory='" + comboBox2.Text + "' and size='" + comboBox3.Text + "'";

但是它给了我以下的异常:

IErrorInfo。GetDescription failed with E_FAIL(0x80004005).

你能帮我吗?

完整代码:

connection.Open(); 
OleDbCommand command = new OleDbCommand(); 
command.Connection = connection; 
string query = "select * from products where category='" + comboBox1.Text + 
    "' and subcategory='" + comboBox2.Text + "' and size='" + comboBox3.Text + "'"; 
command.CommandText = query; 
OleDbDataAdapter da = new OleDbDataAdapter(command); 
DataTable dt = new DataTable(); 
da.Fill(dt); 
dataGridView1.DataSource = dt; 
connection.Close();