c#.net datagridview值传到textbox修改，更新数据库，得根据主键ID来确定是否更新该记录
strSql.Append("update Pocket_book set");
if (rdoIncome.Checked)
{
strSql.Append(" IO_Project = '" + cboIncome.Text + "'");
}
else
{
strSql.Append(" IO_Project = '" + cboOutcome.Text + "'");

}
if (Convert.ToDouble(txtMoney.Text) == 0)
{
strSql.Append(" ,Output_Money = '" + txtMoney.Text + "'");
}
else
{
strSql.Append(" ,Input_Money = '" + txtMoney.Text + "'");
}
strSql.Append(" ,IO_date = '" + dtpkDate.Text + "'");
strSql.Append(" ,Project_Explain = '" + txtExplain.Text + "'");
strSql.Append(" where ");
strSql.Append(" Main_ID = " + strMain_ID);<-------出错 说没有定义“strMain_ID”

但是我在前面定义了：
public partial class MyAccountUpdate : Form
{
public MyAccountUpdate()
{

string mainID = string.Empty;
string strExplainName = string.Empty;
string strInMoneyName = string.Empty;
string strOutMoneyName = string.Empty;
string strProjectName = string.Empty;
string strDateName = string.Empty;
string strMain_ID = string.Empty;

InitializeComponent();
}

private void MyAccountUpdate_Load(object sender, EventArgs e)
{

string strInMoneyName = txtMoney.Text;
string strProjectName = txtExplain.Text;
string strOutMoneyName = txtMoney.Text;
string strExplainName = cboIncome.Text;
string strDateName = dtpkDate.Text;
string strMain_ID = txtMain_id.Text;



这是怎么回事啊 在线等！！！！
谢谢了！！！！！！！！！！！！！

[解决办法]
请问你这前后两段代码是否都在 MyAccountUpdate_Load 方法中呢，strMain_ID 是局部变量，如果出了MyAccountUpdate_Load 就无法访问了