Question

我的表单中有一个按钮和一个datagridview。我需要从数据库中获取图像并在datagrid中显示其值，然后在datagrid中获取图像的值以将其复制到另一个数据库。

具体来说，我将图像（blob）从database1的table1复制到database2的表1。

的button1_Click：

Dim img As Image
    Dim bArr As Byte()
Try
            Dim Sql = "Select ID, IMG from sample"
            connectionOnline()
            Dim cmd = New MySqlCommand(Sql, ConOnline)
            Dim dr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
            DataGridView1.Rows.Clear()
            While dr.Read = True
                img = dr(1)
                bArr = imgToByteArray(img)
                DataGridView1.Rows.Add(dr(0), bArr)
            End While
            ConOnline.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

Try
            connectionSync()
            Dim a, b As String
            Dim Sql = "INSERT INTO SAMPLE (ID, IMG)values(@a,@b)"

            For i As Integer = 0 To Me.DataGridView1.Rows.Count - 1
                a = Me.DataGridView1.Rows(i).Cells(0).Value.ToString()
                Dim img1 As Image = byteArrayToImage(bArr)
                Dim cmd As New MySqlCommand(Sql, ConSync)
                cmd.Parameters.AddWithValue("@a", a)
                cmd.Parameters.AddWithValue("@b", img1)
                cmd.ExecuteNonQuery()
                cmd.Parameters.Clear()
            Next
            ConSync.Close()
        Catch ex As Exception
               MsgBox(ex.Message)
        End Try


Try
            connectionSync()
            Dim Sql = "INSERT INTO B.SAMPLE(ID, IMG) SELECT ID, IMG FROM C.SAMPLE WHERE not exists (SELECT 1 from B.SAMPLE WHERE B.SAMPLE.ID=C.SAMPLE.ID)"
            Dim cmd = New MySqlCommand(Sql, ConSync)
            With cmd
                .ExecuteNonQuery()
            End With
            MsgBox("Success", vbInformation, "Save")
            ConSync.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

Try
            connectionOffline()
            Dim Sql = "UPDATE SAMPLE SET IMG=(SELECT C.SAMPLE.NAME FROM C.SAMPLE WHERE C.SAMPLE.ID=B.SAMPLE.ID) WHERE B.SAMPLE.ID=(SELECT C.SAMPLE.ID FROM C.SAMPLE WHERE C.SAMPLE.ID=B.SAMPLE.ID)"
            Dim cmd = New MySqlCommand(Sql, ConOffline)
            With cmd
                .ExecuteNonQuery()
            End With
            MsgBox("Success")
            ConOffline.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

B和C是数据库
虽然样本是表格

下面是我用来转换图像的功能

Public Function imgToByteArray(ByVal img As Image) As Byte()
        Using mStream As New MemoryStream()
            img.Save(mStream, img.RawFormat)
            Return mStream.ToArray()
        End Using
    End Function

    Public Function byteArrayToImage(ByVal byteArrayIn As Byte()) As Image
        Using mStream As New MemoryStream(byteArrayIn)
            Return Image.FromStream(mStream)
        End Using
    End Function

结果（在数据库中; IMG）仅显示：＆＃34; System.Drawing.Bitmap ＆＃34;而不是实际的图像

Answer 1

您只存储“Image.ToString”。

尝试使用二进制参数：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

void ret_2darr(char *(*str)[5])
{
    int i,j;
    for(i=0;i<3;i++)
    {
        for(j=0;j<=5;j++)
        {
            str[i][j]=(char *)malloc(sizeof("sach"));
            strcpy(str[i][j],"sach");
        }
    }
}

main()
{
    char *(*a)[5]=NULL;
    ret_2darr(a);
    int i,j;
    for(i=0;i<3;i++)
    {
        for(j=0;j<=5;j++)
        {
            printf("%s",a[i][j]);
        }
    }
 }

将图像从数据库转换为字节并返回图像时出现问题

1 个答案: