System.Data.dll中出现“System.Data.SqlClient.SqlException”类型的exception

我是c＃的初学者，当我执行代码时出现此错误消息>>

“System.Data.dll中出现’System.Data.SqlClient.SqlException’类型的exception，但未在用户代码中处理

附加信息：’=’附近的语法不正确。 “

这是代码!!

string position; SqlConnection con = new SqlConnection("server=free-pc\\FATMAH; Integrated Security=True; database=Workflow; "); con.Open(); SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID=" + id.Text, con); SqlDataReader Read = cmd.ExecuteReader(); if (Read.Read()==true) { position = Read[0].ToString(); Response.Write("User Registration successful"); } else { Console.WriteLine("No Employee found."); } Read.Close(); 

Answer 1

您的代码存在一些问题。 首先，我建议使用参数化查询，以避免SQL注入攻击，并且框架也会发现参数类型：

 var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con); cmd.Parameters.AddWithValue("@id", id.Text); 

其次，因为您只对从查询返回的一个值感兴趣，所以最好使用ExecuteScalar MSDN ：

 var name = cmd.ExecuteScalar(); if (name != null) { position = name.ToString(); Response.Write("User Registration successful"); } else { Console.WriteLine("No Employee found."); } 

最后一件事是将SqlConnection和SqlCommand包装成using以便那些using资源处理掉：

 string position; using (SqlConnection con = new SqlConnection("server=free-pc\\FATMAH; Integrated Security=True; database=Workflow; ")) { con.Open(); using (var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con)) { cmd.Parameters.AddWithValue("@id", id.Text); var name = cmd.ExecuteScalar(); if (name != null) { position = name.ToString(); Response.Write("User Registration successful"); } else { Console.WriteLine("No Employee found."); } } } 

Answer 2

我认为您的EmpID列是字符串 ，您忘记在您的值中使用' ' 。

因为当您编写EmpID=" + id.Text ，您的命令看起来像EmpID = 12345而不是EmpID = '12345'

将您的SqlCommand更改为

 SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID='" + id.Text +"'", con); 

或者作为一种更好的方式，您可以（并且应该）始终使用parameterized queries 。 这种字符串连接对SQL Injection攻击是开放的。

 SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con); cmd.Parameters.AddWithValue("@id", id.Text); 

我认为您的EmpID列保留了您的员工ID，因此它的类型应该是一些数字类型而不是字符。

Answer 3

试试这个

 SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID=@id", con); cmd.Parameters.AddWithValue("id", id.Text); 

Answer 4

System.Data.dll中发生了未处理的“System.Data.SqlClient.SqlException”类型exception

  private const string strconneciton = "Data Source=.;Initial Catalog=Employees;Integrated Security=True"; SqlConnection con = new SqlConnection(strconneciton); private void button1_Click(object sender, EventArgs e) { con.Open(); SqlCommand cmd = new SqlCommand("insert into EmployeeData (Name,S/O,Address,Phone,CellNo,CNICNO,LicenseNo,LicenseDistrict,LicenseValidPhoto,ReferenceName,ReferenceContactNo) values ( '" + textName.Text + "','" + textSO.Text + "','" + textAddress.Text + "','" + textPhone.Text + "','" + textCell.Text + "','" + textCNIC.Text + "','" + textLicenseNo.Text + "','" + textLicenseDistrict.Text + "','" + textLicensePhoto.Text + "','" + textReferenceName.Text + "','" + textContact.Text + "' )", con); cmd.ExecuteNonQuery(); con.Close(); } 

Answer 5

使用try-catch查看发生的真实错误

  try { //Your insert code here } catch (System.Data.SqlClient.SqlException sqlException) { System.Windows.Forms.MessageBox.Show(sqlException.Message); } 

Answer 6

 using (var cmd = new SqlCommand("SELECT EmpName FROM [Employee] WHERE EmpID = @id", con)) 

把[]放在表名周围;）