Question

我有以下代码，它连接到Sql数据库并将数据插入表中：

string firstNameV = txtFname.Text;
string surnameV = txtSname.Text;
string emailV = txtEmail.Text;

SqlConnection conn = new   SqlConnection(ConfigurationManager.ConnectionStrings["myConnectionString"].ToString());

SqlCommand cmd = new SqlCommand();

cmd.CommandText = "INSERT INTO EmailSignUp (Title,FirstName,Surname,Email,EstablishmentType,Interests) VALUES (@Title,@FirstName,@Surname,@Email,@EstablishmentType,@Interests)";

cmd.Parameters.Add("@Title", SqlDbType.NVarChar).Value = title;
cmd.Parameters.Add("@FirstName", SqlDbType.NVarChar).Value = firstNameV;
cmd.Parameters.Add("@Surname", SqlDbType.NVarChar).Value = surnameV;
cmd.Parameters.Add("@Email", SqlDbType.NVarChar).Value = emailV;
cmd.Parameters.Add("@EstablishmentType", SqlDbType.NVarChar).Value = eType;
cmd.Parameters.Add("@Interests", SqlDbType.NVarChar).Value = ins;

cmd.Connection = conn;

conn.Open();

cmd.ExecuteNonQuery();
conn.Close();

如何检查是否在＆＃34; txtEmail＆＃34;中输入了电子邮件？文本框已经存在于我的数据库中，在电子邮件列中，然后是警告消息，说电子邮件已经存在，因此它不会插入到我的数据库中？

Answer 1

在必需的文本框或区域中调用此方法

public void EmailCheck()
    {
        string constring = ConfigurationManager.ConnectionStrings["ConnData"].ConnectionString;
        SqlConnection con = new SqlConnection(constring);
        SqlCommand cmd = new SqlCommand("Select * from EmailSignUp where EmailId= @EmailId", con);
        cmd.Parameters.AddWithValue("@EmailId", this.txtEmail.Text);
        con.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            if (dr.HasRows == true)
            {
                MessageBox.Show("EmailId = " + dr[5].ToString() + " Already exist");
                txtEmail.Clear();
                break;
            }
        }

    }

Answer 2

试试这个

cmd.CommandText = "IF NOT EXISTS(SELECT * FROM EmailSignUp WHERE Email = '" 
+ txtEmail.Text + "') 
BEGIN
INSERT INTO EmailSignUp (Title,FirstName,Surname,Email,EstablishmentType,Interests) VALUES (@Title,@FirstName,@Surname,@Email,@EstablishmentType,@Interests) 
END";

Answer 3

调用存储过程并在存储过程内部进行检查在插入之前

 IF NOT EXISTS(SELECT * FROM EmailSignUp WHERE Email =@email)   
 Begin
insert query here
 end

另一方面，您可以在文本更改事件中检查

Answer 4

在SQL Server上创建一个过程并检查名称是否存在

    CREATE PROCEDURE Procedure_Name 
@mystring varchar(100),
@isExist bit out
AS
BEGIN
    if exists(select column1 from tblTable1 where column1=@mystring)
    begin
    select @isExist=1
    end
    else
    begin
    select @isExist=0
    end


END
GO

这是一个示例程序。如果@ isExist = 1表示该值存在，则表示不存在。创建一个方法来调用此过程并继续... 快乐编码

如何检查数据库中是否已存在值并显示验证消息

4 个答案: