字典中不存在给定的键。与 mysql

Question

我正在尝试将C#中的项目与MySQL ( localhost ) 链接，但在执行登录时出现错误

System.Collections.Generic.KeyNotFoundException was unhandled
HResult=-2146232969
Message=The given key was not present in the dictionary.
Source=mscorlib
StackTrace:
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
at MySql.Data.MySqlClient.CharSetMap.GetCharacterSet(DBVersion version, String CharSetName)
at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData41()
at MySql.Data.MySqlClient.NativeDriver.GetFieldMetaData()
at MySql.Data.MySqlClient.NativeDriver.ReadColumnMetadata(Int32 count)
at MySql.Data.MySqlClient.ResultSet.LoadMetaData()
at MySql.Data.MySqlClient.ResultSet.NextResult()
at MySql.Data.MySqlClient.MySqlDataReader.NextResult()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()
at College_Student.login.button1_Click(Object sender, EventArgs e) in C:\Users\zMJ\Desktop\College_Student\College_Student\login.cs:line 87
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)

这就是我尝试的连接

 MySqlConnection con = new MySqlConnection(" Server=localhost;Database=college_management;Uid=root;Pwd=12345678;CharSet=utf8;");

并使用库

    using MySql.Data.MySqlClient;
using System.Data;

并在按钮中

private void button1_Click(object sender, EventArgs e)
{
    i=0;
    con.Open();
    MySqlCommand cmd = con.CreateCommand();
    cmd.CommandType = CommandType.Text;
    cmd.CommandText = "SELECT * FROM  admins where name='" + textBox1.Text + "' and password='" + textBox2.Text + "' ";
    cmd.ExecuteNonQuery();
    DataTable dt = new DataTable();
    MySqlDataAdapter da = new MySqlDataAdapter(cmd);
    da.Fill(dt);
    i = Convert.ToInt32(dt.Rows.Count.ToString());

    if (i == 0)
    {
        MessageBox.Show("error");
    }
    else
    {
        this.Hide();
        new home().Show();

    }

    con.Close();
            }

Answer 1

该问题似乎是由于使用 Connector/NET 不支持的字符集（对于您的数据库或列）引起的。（例如，请参阅MySQL bug 58244。）这通常可以通过从 NuGet 更新到库的最新版本来解决。

如果您已经在运行最新版本的 Connector/NET，请尝试切换到MySqlConnector，这是一个更可靠的C# MySQL ADO.NET 库。