如何避免通过winform将重复值输入表中？ [英] How to avoid entering duplicate values into table through winform?

问题描述

在我的项目中我已将客户端名称设置为主键，如果我输入相同的值，我将获得异常，现在我想编写验证，即如果我重新输入主键值，那么我应该得到一个像数据已存在这样的消息，请帮我这样做，我用来插入值的代码是：

in my project I have set the client name as primary key and if I enter the same value, I will get exception, now I want to write the validation, i.e if I re enter the primary key value then I should get a message like "Data already exists", Please help me to do that, The code I am using to insert value is:

  private void btnInsert_Click(object sender, EventArgs e)
   {
    if (txtName.Text == string.Empty)
    {
        MessageBox.Show("Please enter a value to Project Name!");
        txtName.Focus();
        return;
    }
    if (txtContactPerson.Text == string.Empty)
    {
        MessageBox.Show("Please enter a value to Description!");
        txtContactPerson.Focus();
        return;
    }
    SqlConnection con = Helper.getconnection();
    con.Open();
    string commandText = "InsertClient";
    SqlCommand cmd = new SqlCommand(commandText, con);
    cmd.Parameters.AddWithValue("@Name", txtName.Text);
    cmd.Parameters.AddWithValue("@ContactPerson", txtContactPerson.Text);
    cmd.CommandType = CommandType.StoredProcedure;
    MessageBox.Show("Client details are inserted successfully");
    txtName.Clear();
    txtContactPerson.Clear();
    object Name = cmd.ExecuteNonQuery();
    con.Close();
    BindData();
}

推荐答案

由于您已将客户端名称作为主键，因此SqlException将对其进行验证重复的客户名称。



像这样更改你的代码。

Since you have given client name as primary key the SqlException will make the validation for the duplicate Client Name.

Change your code like this.

try
{
    object Name = cmd.ExecuteNonQuery();
}
catch(SqlException sqlex)
{
    if(sqlex.Number == 2601 || sqlex.Number == 2627)
    {
        MessageBox.Show("Client Name already exists!");
        txtContactPerson.Focus();
    }
}
finally 
{    
    if(con!= null)  
    { 
       con.Close(); 
    }
} 

Thomas Sir已经给出了解决方案，但这里有另一个解决方案，您可以在插入数据之前检查名称，如果名称不是存在然后插入数据

Thomas Sir has given solution but here is another solution that you can check name before inserting data and if name not exists then insert data

private void btnInsert_Click（object sender，EventArgs e）

{

if（txtName.Text == string） .Empty）

{

MessageBox.Show（请输入项目名称的值！）;

txtName.Focus（）;

返回;

}

if（txtContactPerson.Text == string.Empty）

{

MessageBox.Show（请输入一个值来描述！）;

txtContactPerson.Focus（）;

return;

}

SqlConnection con = Helper.getconnection（）;

con.Open（）;

尝试

{

string commandText =InsertClient;

SqlCommand cmd = new SqlCommand（commandText，con）;

cmd.Parameters.AddWithValue（@ Name，txtName.Text）;

cmd.Parameters.AddWithValue（@ ContactPerson，txtContactPerson.Text）;

cmd.CommandType = CommandType.StoredProcedure;



MessageBox.Show（客户端详细信息已成功插入）;

txtName.Clear（） ;

txtContactPerson.Clear（）;



object Name = cmd.ExecuteNonQuery（）;

BindData（ ）;

}

catch（例外情况）

{



MessageBox .Show（ex.Message）;



}

finall y

{

con.Close（）;

}

}

private void btnInsert_Click(object sender, EventArgs e)
{
if (txtName.Text == string.Empty)
{
MessageBox.Show("Please enter a value to Project Name!");
txtName.Focus();
return;
}
if (txtContactPerson.Text == string.Empty)
{
MessageBox.Show("Please enter a value to Description!");
txtContactPerson.Focus();
return;
}
SqlConnection con = Helper.getconnection();
con.Open();
try
{
string commandText = "InsertClient";
SqlCommand cmd = new SqlCommand(commandText, con);
cmd.Parameters.AddWithValue("@Name", txtName.Text);
cmd.Parameters.AddWithValue("@ContactPerson", txtContactPerson.Text);
cmd.CommandType = CommandType.StoredProcedure;

MessageBox.Show("Client details are inserted successfully");
txtName.Clear();
txtContactPerson.Clear();

object Name = cmd.ExecuteNonQuery();
BindData();
}
catch (Exception ex)
{

MessageBox.Show(ex.Message);

}
finally
{
con.Close();
}
}

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