SqlCommand com = new SqlCommand( );
            com.Connection =con;
            com.Parameters.Add("@v1",SqlDbType.VarChar,50,"品种");
            com.Parameters.Add("@v2",SqlDbType.Int,4,"农户ID");
            com.Parameters.Add("@v3",SqlDbType.Decimal ,9,"收购价");
            com.Parameters.Add("@v4",SqlDbType.DateTime ,8,"成熟时间");
            com.Parameters.Add("@v5",SqlDbType.Decimal ,9,"数量");
            com.Parameters["@v1"].Value = TextBox1.Text;
            com.Parameters["@v2"].Value = TextBox2.Text;
            com.Parameters["@v3"].Value = TextBox3.Text;
            com.Parameters["@v4"].Value = TextBox4.Text;
            com.Parameters["@v5"].Value = TextBox5.Text;
            com.CommandText = "select * from farmer where 品种=@v1and农户ID=@v2and收购价=@v3and成熟时间=@v4and数量=@v5";
            SqlDataReader dr=com.ExecuteReader ();  提交的时候老是显示字符串格式不对这个格式有哪儿不对吗？

试试单引号