明天就要交给老大了，急，在线等

Question

 private void timer1_Tick(object sender, EventArgs e)
        {
            int a=0;//　　为了符合数据库类型　，可空类型；
            
            Form4 mm = new Form4();
            SqlConnection sqlconn = new SqlConnection(@"server=(local);database=xmgl;uid=sa;pwd=;Connection Timeout=30");
            sqlconn.Open();
            
            SqlCommand sqlcomm = new SqlCommand("select * from money",sqlconn);            SqlDataReader sqlread = sqlcomm.ExecuteReader();
            while(sqlread.Read())
            {
                //a = (int)sqlread.GetValue(4);
                a = Convert.ToInt32(sqlread[4].ToString());                       /这里显示输入字符串格式不对
                if(a==0)
                {
                   DateTime b=Convert.ToDateTime(sqlread[5].ToString());
                    if(DateTime.Now>b)
                    {
                        mm.Show();
                    }
                }
                if(a==1)
                {
                    DateTime b = Convert.ToDateTime(sqlread[6].ToString());
                     if(DateTime.Now>b)
                    {
                        mm.Show();
                    }
                }
                if (a == 2)
                {
                    DateTime b = Convert.ToDateTime(sqlread[7].ToString());
                     if(DateTime.Now>b)
                    {
                        mm.Show();
                    }
                }
                if (a > 2 && a <= 4)
                {
                    DateTime b = Convert.ToDateTime(sqlread[8].ToString());
                     if(DateTime.Now>b)
                    {
                        mm.Show();
                    }
                }
              
            }
}

Answer 1

添加对VB.NET运行时的引用(在引用里添加“Microsoft Visual Basic ...”)，然后做如下处理：
if( Microsoft.VisualBasic.Information.IsNumeric(a)){
a = Convert.ToInt32(sqlread[4].ToString());                      /这里显示输入字符串格式不对 
...
}

Answer 2

  a = (strint)sqlread[4].ToString());                      /这里显示输入字符串格式不对 

Answer 3

  a = (string)sqlread[4].ToString());                      /这里显示输入字符串格式不对 

Answer 4

更正一下：应该是if( Microsoft.VisualBasic.Information.IsNumeric(sqlread[4])){

Answer 5

a = Convert.ToInt32(sqlread.GetValue(4));

Answer 6

你是说数据库字段可以为空吧？
为空的的话Convert方法肯定出錯了。加个判断，为空的话赋为0：
a = (sqlread[4].ToString()=="" ? 0 : Convert.ToInt32(sqlread[4]));