[英]Catching an Exception in C#
我有一個簡單的按鈕ADD
而ADD_Click代碼是:
protected void Add_Click(object sender, EventArgs e)
{
string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;
SqlConnection myConnection = new SqlConnection(strConnectionString);
myConnection.Open();
string hesap = Label1.Text;
string musteriadi = DropDownList1.SelectedItem.Value;
string avukat = DropDownList2.SelectedItem.Value;
SqlCommand cmd = new SqlCommand("INSERT INTO AVUKAT VALUES (@MUSTERI, @AVUKAT, @HESAP)", myConnection);
cmd.Parameters.AddWithValue("@HESAP", hesap);
cmd.Parameters.AddWithValue("@MUSTERI", musteriadi);
cmd.Parameters.AddWithValue("@AVUKAT", avukat);
cmd.Connection = myConnection;
SqlDataReader dr = cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
Response.Redirect(Request.Url.ToString());
myConnection.Close();
}
我想要的是,如果有人添加具有相同HESAP
(主鍵)的數據,我想要一個帶有這個詞的alert()函數。 “已經有相同的數據”或任何文字。 無所謂。
我怎樣才能做到這一點?
注意 :我只想獲得相同的HESAP值並捕獲錯誤。
嘗試這個:
protected void Add_Click(object sender, EventArgs e)
{
string hesap = Label1.Text;
string musteriadi = DropDownList1.SelectedItem.Value;
string avukat = DropDownList2.SelectedItem.Value;
string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;
using (SqlConnection myConnection = new SqlConnection(strConnectionString))
{
myConnection.Open();
using (SqlCommand cmd = new SqlCommand("INSERT INTO AVUKAT VALUES (@MUSTERI, @AVUKAT, @HESAP)", myConnection))
{
cmd.Parameters.AddWithValue("@HESAP", hesap);
cmd.Parameters.AddWithValue("@MUSTERI", musteriadi);
cmd.Parameters.AddWithValue("@AVUKAT", avukat);
cmd.Connection = myConnection;
try
{
cmd.ExecuteNonQuery();
}
catch (SqlException ex)
{
if (ex.Number == 2627)
{
// Add a javascript alert to let the user know that the same HESAP value already exists.
}
else
{
// Rethrow the exception.
throw;
}
}
}
Response.Redirect(Request.Url.ToString());
myConnection.Close();
}
}
您可以先添加另一個查詢,使用簡單的select語句檢查密鑰是否存在,或者您可以(uglier solution imo)嘗試/捕獲如果存在主鍵沖突,ExecuteReader將拋出的SqlException。
我假設數據庫將同時擁有多個用戶。
正如安德烈亞斯所提到的,我建議對SQLException執行try / catch以獲取主鍵沖突。 我會建議兩個查詢,因為應用程序流(來自不同的用戶)可能如下所示:
try
{
//open connection
//Insert
}
catch(SQLException Excep)
{
//If primary key violation alert()
}
finally
{
//Close connection
}
這可能對你有幫助
雖然可以而且應該對其他用戶所指出的原始代碼(使用語句,ExecuteNonQuery等)進行一些改進,如果您只想檢測主鍵約束違規,那么您可以檢查錯誤編號。 catch塊中的SqlException。 錯誤編號為2627.使用現有代碼,它看起來像這樣......
try
{
string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;
SqlConnection myConnection = new SqlConnection(strConnectionString);
myConnection.Open();
string hesap = Label1.Text;
string musteriadi = DropDownList1.SelectedItem.Value;
string avukat = DropDownList2.SelectedItem.Value;
SqlCommand cmd = new SqlCommand("INSERT INTO AVUKAT VALUES (@MUSTERI, @AVUKAT, @HESAP)", myConnection);
cmd.Parameters.AddWithValue("@HESAP", hesap);
cmd.Parameters.AddWithValue("@MUSTERI", musteriadi);
cmd.Parameters.AddWithValue("@AVUKAT", avukat);
cmd.Connection = myConnection;
SqlDataReader dr = cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
Response.Redirect(Request.Url.ToString());
myConnection.Close();
}
catch (SqlException ex)
{
if (ex.Number == 2627)
{
// Add a javascript alert to let the user know that the same HESAP value already exists.
}
else
{
// Rethrow the exception.
throw;
}
}
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